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Genetic Testing, Essay Example

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Genetic testing also known as DNA-based testing involves examining DNA molecules to find possible signs of genetic disorders. The advancements in the field of genetics have rapidly pushed the boundaries of medical science and have made it possible to predict the probability of genetic disorders to occur in the individuals. Thus, the greatest promise of genetic testing is not only in preventive measures but further advancements in genetics are expected to produce techniques that may even be able to repair faulty genes. Currently, there are more than 1000 genetic tests available from the testing laboratories including Alzheimer’s disease, Cystic fibrosis, Huntington’s disease, Sickle cell disease, and Timothy Syndrome.

As with any disruptive technology, the genetic testing raises certain ethical and moral issues. Privacy is one of the major concerns because genetic testing results could be used by insurance companies and other commercial enterprises to decide whether to provide their services or not and may charge more to the customers they perceive as high-risk. In addition, genetic testing is not fool-proof and the misleading results may lead to inaccurate treatments and preventive measures. In addition, the technology is still in infancy and any information that can’t be interpreted with reliability even if it’s accurate is as useless as no information at all. The medical community has no professional standards or guidelines that could be used to analyze the genetic testing results which results in doctors applying inconsistent analytical tools and reaching inconsistent conclusions.

The results of the genetic testing may inflict emotional pain on the individuals even if they are inaccurate. The psychosocial risks may be guilt, anxiety, impaired self-esteem, social stigma, and employment discrimination (American Academy of Pediatrics). There may be financial risks if the customer decides to act on the information and opt for expensive medical treatments in hope of reducing the risks indicated by genetic test. Moreover, genetic information has limited predictive power as our genes interact with the environment in complex ways.

As far as genetic testing in pediatrics is concerned, the American Academy of Pediatrics recommends genetic testing only when it is in the best interests of the child and when the legitimate interests of the parent and the family can be promoted without anticipated harm to the child. It has been argued that genetic testing for children should be mandatory because a society has an obligation to promote child welfare through detective and timely treatment of selected conditions. At the same time, parents have a tendency to underestimate the risks involved in treatments on the basis of genetic test which may not promote the best interests of the child (American Academy of Pediatrics).

Emory Law Journal provides an interesting hypothesis on the potential impact of media on consumer choices. American actress Christina Applegate appeared on the Oprah Winfrey show on September 30, 2008 and declared that her decision to remove both of her breasts was based on her genetic test. She remarked, “I’m clear. Absolutely 100 percent clear and clean.” This information could be misinterpreted by the female viewers who have a family history of breast cancer. They may order their genetic test and decide to go the Christina Applegate way. But Christina Applegate’s self-assurance was not exactly correct because double mastectomy significantly decreases the chance of later developing breast cancer but does not guarantee prevention. In addition, direct-to-consumer companies have no obligation to tell customers of the treatment choices available and the customers may underestimate the social and emotional distress that breast removal may cause them later. Direct-to-consumer companies have a potential to mislead customers because even though they issue disclaimer that their results cannot be used to make medical decisions and that the users assume all the risk, their marketing messages send hope and promise of healthy future. Genetic testing companies are avoiding the possibility of legal problems by masking themselves as seller of informational and recreational services (Kishore, 2010).

The pace of regulations to govern the trade practices of the direct-to-consumer companies may have yet to come but the issue has not escaped the attention of the government. United States Government Accountability Office (GAO) tested direct-to-consumer genetic testing companies and found that they made medically unproven claims. In addition, the results from all the four companies whose services GAO purchased yielded results that were inconsistent with each other and the companies didn’t inform of their inability to carry out DNA tests on races prior to the purchase. In addition, the individual companies yielded different test results on the two samples that were actually the same. Some companies even tried to sell supplements that were supposed to repair damaged DNAs. In addition, they used fraudulent endorsements from high profile athletes (Kutz). This shows that genetic testing is still unreliable and a huge risk exists in utilizing genetic tests for making important medical decisions.

There is also a risk that genetic tests may be abused by employers to predict the probability of undesirable behavior in individuals which may or may never happen. For example, if an individual possesses a gene variant which studies link to increase risk of substance abuse such as alcohol and drugs, the employer may decide he doesn’t want to hire a potential future liability (Bailey).

Genetic testing may have limited useful and reliable applications especially in the case of diseases whose genes are few and have been correctly identified. Huntington gene is one example. People with Huntington disease have 36 to more than 120 CAG (Huntington disease is also known as CAG trinucleotide repeat expansion). People with 36 to 40 CAG repeats may or may not develop the signs of Huntington disease but people with more than 40 repeats almost always develop the disorder (Genetics Home Reference).

Genetic testing if proved negative may give false hopes to the customers. Customers may become careless with their life habits and may even forego regular diagnosis tests later in life. Thus, just as positive results may result in over reaction, negative results may lead to carelessness on the part of the customers. Genetic tests point towards a bright future of medical science as further progress is made but it will take some time for genetic testing to become a truly reliable medical service. Even when genetic testing is taken, the importance of medical advice should not be underestimated. Medical professionals are better informed due to their experience and knowledge and are better aware of the various options available to the customers.

Genetic testing may have consequences that extend far beyond the individuals. Genetic testing may persuade couples to opt for abortion or totally forego procreation plans. Some people may object on the basis of their moral values that humans are trying to imitate God which could limit federal funding to fund genetic research and slow down the progress in genetics. This has already happened when President Bill Clinton sent bill to the Congress to outlaw the cloning of humans on the recommendation of the National Bioethics Advisory Commission (Human Genome News, 1997).

American Academy of Pediatrics. Ethical Issues With Genetic Testing in Pediatrics. 3 February 2011 <http://aappolicy.aappublications.org/cgi/content/full/pediatrics;107/6/1451>.

Bailey, Ronald. “I’ll Show You My Genome. Will You Show Me Yours?” Reason January 2011: 35-43.

Genetics Home Reference. HTT. October 2008. 3 February 2011 <http://ghr.nlm.nih.gov/gene/HTT>.

Human Genome News. President’s Bill Would Prohibit Human Cloning. January-June 1997. 3 February 2011 <http://www.ornl.gov/sci/techresources/Human_Genome/publicat/hgn/v8n3/07pres.shtml>.

Kishore, Deepthy. “Test at Your Own Risk: Your Genetic Report Card and the Direct-To-Consumer Duty to Secure Informed Consent.” Emory Law Journal 2010: 1553-1609.

Kutz, Gregory. “Direct-To-Consumer Genetic Tests: Misleading Test Results Are Further Complicated by Deceptive Marketing and Other Questionable Practices.” Investigative. 2010.

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Home — Essay Samples — Science — Human Genome Project — The Ethical Implications of Genetic Testing

The Ethical Implications of Genetic Testing

Categories: Bioethics Genetic Modification Human Genome Project

About this sample

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Published: Aug 30, 2022

Words: 3147 | Pages: 7 | 16 min read

Bibliography, genetic testing methods, issues regarding genetic testing.

possible future absence,
conditions that put employees at risk in the work place
if emploees are sensitivity to the environment of the workplace (chemicals allergy etc).

Steps Toward Dealing With the Issues

To define the implications expected of the Human Genome Project for individuals and society.
To examine legal, social and ethical secondary results of the sequencing and mapping of the human genome.
To stimulate public discussion about the identified issues surrounding genetic testing.
To make policy to make sure that the results from the HGP is used for the benefit of society and individuals.
Annas, George J. 'Whoís Afraid of the Human Genome?' National Forum, Spring 93, Vol. 73 p.35-37.
Drlica, Karl A. Double-Edged Sword. Addison-Wesley Publishing Co., New York, 1994.
Elliott, Jeff, 'Genetic Dilemmas.' World & I, Mar95, Vol. 10 p. 212-217.
Heller, Jan Christian. Human Genome Research and the Challenge of Contingent Future Persons. Creighton Univ. Press, Omaha, 1996.
Holloway, Marguerite 'Turning the Inside Out', Scientific American, Jun95, Vol. 272 Issue 6, p49-51.
Hudson, Kathy L., Karen H. Rothenberg, Lori B. Andrews, Mary Jo Ellis Kahn, Francis S. Collins. 'Genetic Discrimination and Health Insurance: An Urgent Need for Reform.' Science. Oct 20, 1995.
Kelves, Daniel J. and Leroy Hood. The Code of Codes. Harvard Univ. Press, Cambridge, 1992.
Lee, Thomas F. Gene Future: The Promise and Perils of the New Biology. Plenum Press, New York, 1993.
Mehlman, Maxwell J. and Jeffery R Botkin. Access to the Genome: The Challenge to Equality. Georgetown Univ. Press, Washington, 1998.
Meilaender, Gilbert, 'Mastering our Gene(i)es: When Do We Say No?' Christian Century, Oct. 3 '90, Vol. 107, No. 27. van Ommen, G. J. B., E Bakker, and J T den Dunnen. 'The Human Genome Project and the Future of
Diagnostics, Treatment, and Prevention'. Lancet , Jul 30 '99, p.354.
Ward, Darrel E., 'Gene Therapy: The Splice of Life.' USA Today Magazine, Jan 93, Vol. 121 p. 63-66.
Zimmern, R.L. 'Genetic Testing: A Conceptual Exploration', Journal of Medical Ethics, Apr 99, Vol 25 p. 151-155.

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Ethics of Genetic Testing

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Bioethics Resources

When what we know outstrips what we can do

Our genes contain information that scientists hope will help in the treatment of many diseases. Huntington's disease provides a window on the choices we face as medicine increases our ability to intervene in human genetics.

Stop pacing, Mom. It'll be all right." Meghan and her mother, Anne, fidget nervously in the waiting area of the genetic testing center.

Anne halts and faces her daughter. "I wish it wasn't this way, Meghan." Anne's family has been haunted by Huntington's since anyone can remember; those who get it always die from it. Her brother Harry was just fine until his mid- 40s—then came the depression, the twitching arms."I need to have this test, Mom," Meghan continues. "I want to know if I'm going to wind up like Uncle Harry. I want to know the chances that my children will inherit Huntington's disease." Meghan and her husband, Rick, want to start a family-a family untouched by Huntington's bizarre dances, frightening mood swings, and untimely death. "I'd rather not have children if it means sentencing them to a death like that," Meghan says.

"I would do anything to spare you," Anne says. "But, Meghan, please understand that I don't want to be tested. 'So far, so good' is my philosophy. I'm only 42. I want to live my life and make my decisions without a Huntington's diagnosis hanging over my head."

"But Mom, you're not the one being tested; I am."

Falling into the chair next to her daughter, Anne pleads, "Don't you see? If your test is positive, it means I've got the gene, too. And I don't want to know. I have a right not to know, don't I?"

Anne and Meghan face a tentative future. Members of families with a history of Huntington's disease have long known that this neurological disorder-with its loss of motor control, personality changes, depression, dementia, and death-might eventually be their fate.

Huntington's is a genetic disease, one that can be passed down from parents to children. The gene for Huntington's is dominant, which means that a single copy of the gene from either parent triggers the disease. Children of people afflicted with Huntington's disease have a 50/50 chance of also having the disease.

Until recently, these people had no way of knowing whether they were in the unlucky 50 percent until symptoms actually appeared, usually between the ages of 30 and 50. Then, in 1993, scientists identified the gene responsible for the disorder and made possible the test Meghan wants to take.

If Meghan is tested and found to carry the gene for Huntington's disease, her mother must also have the gene. Meghan, then, will know what Anne does not want to know. What should Meghan do?

The Human Genome Project

Meghan's problem foreshadows the dilemmas many people will face as scientists learn more about genetics. In 1990, an international effort was launched to decode the language of our genes—the Human Genome Project (HGP). The United States is investing $3 billion over 15 years in this endeavor to map the complete set of genes for humans-the human genome. The project will make it easier for researchers who want to identify the genetic components both of disease and of physical and intellectual traits.

Thus far, the most obvious result of the HGP is the rapid proliferation of genetic information. As the new information pours in, the traditional questions haunt us: What should we do with this information? What does this particular genetic alteration mean personally, medically, and socially? If we can, should we intervene to correct or enhance an individual's genome? And when we cannot intervene, how do we handle diagnostic information in the absence of a cure?

Genetic screening can provide new information, not only for potential Huntington's victims but also for sufferers of the more than 4,000 other diseases of genetic origin. Additional ailments are rooted in the interaction of genes with the environment. All told, genetic disorders are the fourth leading cause of death in the United States.

Discovering the location of a disease-causing gene on a chromosome permits diagnosis before the onset of symptoms. It also allows testing of entire populations to identify carriers as well as those who are affected.

The long-term hope is for a precise molecular correction of the defect so that genetic disease becomes as curable as infectious disease. Such therapy might also prevent genetic pathologies from moving from one generation to the next.

The Rift Between Diagnosis and Cure

Yet despite the progress of the HGP—and, indeed, primarily because of it—disease prediction continues to outpace medicine's ability to treat or cure. The test for Huntington's disease can confirm a mutation in the Huntington's gene, but it offers no treatment for the devastating symptoms. The result is a therapeutic rift between what we know and what we can do.

Meghan and Anne fearfully straddle this crevasse, hoping against hope that it will narrow. However, it seems likely that as information flows from the HGP, this therapeutic rift will continue to enlarge for the foreseeable future. This poses profound and puzzling questions about the limits of medical knowledge and human choice.

Consider the effects of genetic information on people who, like Anne and Meghan, confront Huntington's disease. If they discover they do, in fact, have the Huntington's gene, a shadow is cast over the rest of their lives. A slight misstep becomes an omen of uncontrollable muscle movements. Feeling blue is no longer part of everyday life but a precursor of mental collapse. The person's view of life is irreversibly changed by a set of prophecies about affliction and horrifying death.

In Mapping Fate , Alice Wexler describes what it's like to live with this knowledge:

A dancer with Huntington's disease, in her early forties, described how, long before there were any other symptoms, she began having difficulty learning dance sequences; whereas once she had no problem memorizing complicated routines, she gradually found it more and more difficult to master a series of different steps. Later on she found it increasingly difficult to organize a meal, coordinating the different dishes so that they would all come out together. Living at risk undermines confidence, for there is no way of separating the ordinary difficulties and setbacks of life from the early symptoms of the illness. It is not like any other physical illness, where consciousness can at least continue in the knowledge that one is still oneself, despite severe pain and physical limitation. Huntington's means a loss of identity.

But long before the loss of motor control and identity, those who carry the Huntington's gene may face the loss of jobs and health coverage. Many people from families with a history of genetic disorders fear that if they are tested, the results might become public and cause employers or insurers to exclude them. Laws to prohibit such discrimination are not yet completely in place. This is the prophecy of social and medical doom that Anne is resisting.

Responsibilities to the Next Generation

But her daughter Meghan has a different set of concerns. Genetic knowledge is apt to have its greatest impact not on the lives of those who, like the stumbling dancer, are currently stricken, but on the choices to be made by those who, like Meghan, are contemplating parenthood.

If Meghan does not have the gene, then her child will not have the disease. If she does have the gene, any child she conceives has a 50 percent chance of sharing her fate.

Assuming Meghan learns that she has the Huntington's gene, what should she and her husband do? Should they take their chances with genetic roulette? Should they remain genetically childless? Should they undergo prenatal diagnosis?

Prenatal screening and diagnosis can be accomplished through methods such as amniocentesis. Sometimes genetic testing is coupled with in vitro fertilization in a technique called preimplantation genetic diagnosis (PGD). PGD is currently offered in a limited number of research facilities.

In this method, after the egg is fertilized outside the womb, the embryo is allowed to reach the eight-cell stage of development before a cell is removed. This cell is then tested for genetic components that would predispose the child to a particular disease such as Huntington's. Then, only those embryos that do not contain the disease gene are transferred to the uterus, thereby eliminating the chance of having a child with Huntington's disease.

Whatever the promise of this technique, the cost is far from trivial. It includes the fee for IVF-averaging $8,000 per cycle-plus the cost of genetic testing, which adds an estimated $2,000. Even in the rare cases when IVF expenses are paid by health insurance, the genetic component is not covered.

Costs are also likely to be high in the even more advanced procedures now being proposed. In the future, PGD might identify candidates for emerging techniques such as constructive genetic surgery and embryonic cell cloning. Constructive genetic surgery involves removing the affected gene from an embryo and replacing it with normal genetic material. But this is risky business with a failure rate of 80 percent-far too perilous to perform on a single human embryo.

Through cell cloning, however, scientists could make multiple copies of the embryo they wish to modify, increasing the genetic surgical success rate. Indeed, cellular cloning seems to hold the key to the successful genetic engineering of humans. But to what end?

Is Meghan's wish to prune Huntington's disease from her family tree a justified use of this future technology? Suppose parents wish to eliminate the predisposition to alcoholism. What if they want to increase a child's physical stature or intellectual acumen? Would these be reasonable requests for embryonic genetic intervention?

After all, we send our children to soccer practice and tutoring after they are born; why not give them a genetic head start? Is there an ethically relevant difference between genetic therapy and genetic enhancement?

Questions and Guidelines

Reproductive and genetic technologies are opening new medical and moral frontiers, urging us to think in new ways. As the level of medical diagnosis and treatment shifts from bodies and bones to cells and chromosomes, the level of ethical consideration must do the same.

Reaching ethical conclusions about the new genetics is challenging for two reasons: First, it is inherently difficult to understand the subtleties of genetics and the wealth of data tumbling out of the HGP. Second, it is next to impossible to foresee accurately the implications and consequences-short-term, long-term, and unintended-of intervening in the genetic "stuff of life."

The following questions may help to clarify key issues as genetic medicine comes of age:

1. What is the purpose of taking a particular genetic test? Who is affected by the results?

Some people undergo genetic screening simply to know their predisposition to a particular disease. Others may hope to fix that predisposition. Currently, the diagnosis of numerous genetic diseases or predispositions is possible; in most cases, however, there is no treatment or cure. Care must be taken to ensure that patients understand this rift between diagnosis and treatment and that their expectations of the testing are realistic.

Since it became possible to test for the Huntington's gene, fewer than 15 percent of those at risk have taken the test, even when it was offered free of charge. Most would rather not know. Anne, like many of us, is reluctant to find out about an inevitable future. Perhaps, out of respect for her mother's wishes, Meghan could wait to take the test, hoping that in a few more years, scientists may make progress toward a cure. Perhaps Meghan is particularly good at keeping secrets.

Traditional notions of confidentiality are profoundly challenged by medical tests that tell patients not only about themselves but also about family members. As genetic tests become readily available, respect must be given to those who, like Anne, claim a right to ignorance.

2. Who has control of genetic information?

In this era of rapid communication and data proliferation, absolute confidentiality of medical information no longer seems realistic. In a hospital, anywhere from 60 to 200 people have access to a patient's medical records. The information is also passed along to insurance carriers and health maintenance organizations. Given that complete privacy is not possible, it is important to consider who has access to genetic information and for what purpose.

People questioned about genetic testing worry that insurers will raise rates or refuse to insure them. They express concern that employers will not hire them. There is a general fear that friends and family will treat them differently or abandon them once they are "tarnished" by a deadly gene. Medicine's obligation to do no harm mandates that genetic information be used in ways that help people, not in ways that stigmatize and marginalize them.

3. What does it mean to offer genetic testing and/or therapy in the absence of universal access to health care?

This is a question of justice. What counts as a fair share of the health care pie for the poor or for those without health insurance? We live in an era of limited access to childhood immunizations and routine preventive care-both of which are relatively inexpensive and medically effective. As we pour health care dollars into genetic research and treatment, we must also seek to provide basic care to those who are most vulnerable to the ravages of disease: the poor and their children.

4. On what basis should someone undertake genetic intervention such as genetic constructive surgery if and when it becomes available?

Two approaches to this question are possible. One is therapeutic; that is, such techniques should be used to correct particular diseases. The other is eugenic; that is, genetic intervention is permissible to enhance specific characteristics (e.g., intellect) or to give individuals capacities they might not otherwise have had (e.g., playing piano).

The distinction between therapy and enhancement may turn on intention. Is the purpose of the intervention to bring a person to a state of health or to go beyond health in the design of someone new or better?

With the fledgling capacity to alter the human genome comes the responsibility to think carefully about what we consider a benefit for individuals and society. Test tube racks filled with "designer genes" hold not only the promise of molecular treatments but also the age-old mischief of discrimination and exclusion. We are not yet free of the specter of forced eugenicsÑwitness reports that up until the 1970s, an estimated 60,000 people had been sterilized in Sweden under government policies to weed out traits such as poor eyesight and "Gypsy features." What some consider desirable traits may not be a benefit in the eyes of either humanity as a whole or the affected individual.

5. For what kind of genetic future are we planning?

Genetics, by its very nature, embodies a concern for coming generations. Genetic diagnosis and intervention hold great promise. However, we need to consider carefully the power conferred on us by knowing our genetic identity and being able to alter it.

With great power comes greater responsibility, asking us to think carefully about the dramatic impact that genetic information and intervention might have on the future. We face not a red light but a flashing yellow as we enter the age of genetic medicine.

Margaret R. McLean is the director of biotechnology and health care ethics at the Markkula Center for Applied Ethics.

This article was originally published in Issues in Ethics - V. 9, N. 2 Spring 1998.

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The genetic basis of disease

Affiliations.

1 School of Medicine, Dentistry and Nursing, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
2 School of Medicine, Dentistry and Nursing, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K. [email protected].
3 School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
PMID: 30509934
PMCID: PMC6279436
DOI: 10.1042/EBC20170053
Correction: The genetic basis of disease. Jackson M, Marks L, May GHW, Wilson JB. Jackson M, et al. Essays Biochem. 2020 Oct 8;64(4):681. doi: 10.1042/EBC20170053_COR. Essays Biochem. 2020. PMID: 32720679 Free PMC article. No abstract available.

Genetics plays a role, to a greater or lesser extent, in all diseases. Variations in our DNA and differences in how that DNA functions (alone or in combinations), alongside the environment (which encompasses lifestyle), contribute to disease processes. This review explores the genetic basis of human disease, including single gene disorders, chromosomal imbalances, epigenetics, cancer and complex disorders, and considers how our understanding and technological advances can be applied to provision of appropriate diagnosis, management and therapy for patients.

Keywords: cancer; genetics; genomics; molecular basis of health and disease.

PubMed Disclaimer

Conflict of interest statement

The authors declare that there are no competing interests associated with the manuscript.

Figure 1. Some types of variants found…

Figure 1. Some types of variants found in human genomes

Variation involving one or a…

Figure 2. Giemsa banding (G-banding) to form…

Figure 2. Giemsa banding (G-banding) to form a karyogram

( A ) Metaphase spreads like…

Figure 3. Chromosome structure and band nomenclature

This ideogram of the complete chromosome 8 illustrates…

Figure 4. Principles of meiosis and non-disjunction

For simplicity, only one pair of newly replicated…

Figure 5. Fertilisation outcomes

( A ) Fertilisation of a normal oocyte with a normal…

Figure 6. Segregation of reciprocal translocations

( A ) A carrier of a reciprocal translocation…

Figure 7. The X and Y chromosomes…

Figure 7. The X and Y chromosomes determine male or female sexual development

Males produce…

Figure 8. Schematic map of the X…

Figure 8. Schematic map of the X and Y chromosomes

The X and Y chromosomes…

Figure 9. The XIC

A simplified view…

A simplified view of genes located at the XIC (not to…

Figure 10. Autosomal dominant inheritance and pedigree

( A ) Inheritance pattern of an autosomal…

Figure 11. Autosomal recessive inheritance and pedigree

Figure 12. X-linked recessive inheritance and pedigree

( A ) Inheritance pattern of an X-linked…

Figure 13. Insertions and deletions

( 1 ) A wild-type sequence consisting of three-letter words.…

Figure 14. CF symptoms depend on residual…

Figure 14. CF symptoms depend on residual CFTR activity

The left-hand side shows a scale…

Figure 15. Mitochondrial structure

The mitochondrion has…

The mitochondrion has two membranes; the inner membrane folds into series…

Figure 16. The electron transport chain

On the inner membrane of the mitochondria, electrons from…

Figure 17. The mitochondrial genome

Circular and…

Circular and double stranded, with no introns, the mitochondrial genome…

Figure 18. Mitochondrial inheritance

In the case…

In the case of a mitochondrial mutation (see following section), an…

Figure 19. Heteroplasmy

A primordial germ cell…

A primordial germ cell containing a mixture of mutant and normal mtDNA…

Figure 20. Mitochondrial replacement therapy (‘three-parent baby’)

Eggs are harvested ( 1 ) from the…

Figure 21. Methylation of cytosine and consequences…

Figure 21. Methylation of cytosine and consequences of deamination of methyl-C

( A ) Cytosine…

Figure 22. Methylation occurs on the C…

Figure 22. Methylation occurs on the C of the sequence CG and facilitates binding of…

Figure 23. Methylation and demethylation

The methylation…

The methylation process is initiated by addition of a methyl…

Figure 24. DNA methylation status is heritable…

Figure 24. DNA methylation status is heritable but requires maintenance

( A ) The Cs…

Figure 25. Chromatin status is influenced by…

Figure 25. Chromatin status is influenced by DNA methylation and histone acetylation

In active chromatin…

Figure 26. Imprints are erased and reset…

Figure 26. Imprints are erased and reset during gametogenesis

For each imprinted chromosome region, healthy…

Figure 27. Imprinting on chromosome 15

A cluster of genes near the centromere of chromosome…

Figure 28. The principles of genetic association

SNP1 (with alleles C and T) and SNP2…

Figure 29. Genome wide association study for…

Figure 29. Genome wide association study for T2D-related loci

Appropriate study groups are selected from…

Figure 30. Many factors, environmental, genetic and…

Figure 30. Many factors, environmental, genetic and epigenetic interact together in the overall risk for…

Figure 31. Different cancer types typically display…

Figure 31. Different cancer types typically display different numbers of mutations in the cell genome

Figure 32. Cancer increases with age

Theoretical…

Theoretical cancer incidence curves are shown reflecting a set…

Figure 33. Signal transduction

The cell receives…

The cell receives signals from contact with other cells, from the…

Figure 34. A simplified, typical signal transduction…

Figure 34. A simplified, typical signal transduction pathway

Many growth factors (secreted proteins) interact with…

Figure 35. Oncogenic mutations

Examples of oncogene…

Examples of oncogene activating mutations are depicted. ( A ) Gene…

Figure 36. RAS activation

( A ) RAS is bound to GDP in the inactive…

Figure 37. The cell cycle and RB

The cell cycle is depicted, showing the phases…

Figure 38. Sensing and responding to damaged…

Figure 38. Sensing and responding to damaged DNA

The proteins that initiate DNA repair after…

Figure 39. FISH

( A ) One or more fluorescently labelled probes are required for…

Figure 40. Allele-specific PCR by positioning the…

Figure 40. Allele-specific PCR by positioning the variant at the 3′ end of one primer

Figure 41. The MLPA assay and application…

Figure 41. The MLPA assay and application to diagnosis of DGS

( A ) Short…

Figure 42. Automated Sanger sequencing

( A ) PCR products ( 1 ) are generated…

Figure 43. QF-PCR

Several microsatellite loci (here…

Several microsatellite loci (here R, S and T) on the relevant chromosome(s)…

Figure 44. Selecting an appropriate test

Where the pathogenic variant in a family is known…

Figure 45. Basic microarray

The microarray (…

The microarray ( 1 ) is a grid of hundreds of…

Figure 46. SNP array data can reveal…

Figure 46. SNP array data can reveal copy number imbalance and homozygosity associated with consanguinity…

Figure 47. SNP array demonstrates areas of…

Figure 47. SNP array demonstrates areas of loss and gain across the genome at high…

Figure 48. NGS data analysis

The screenshots…

The screenshots cover one exon from the analysis of a…

Figure 49. Amniocentesis procedure

Under ultrasound guidance,…

Under ultrasound guidance, a thin needle is passed through the abdominal…

Figure 50. NIPD for trisomy 21

( A ) Foetal cell-free DNA (cfDNA) from the…

Figure 51. Pre-implantation genetic diagnosis by biopsy…

Figure 51. Pre-implantation genetic diagnosis by biopsy of early embryos

Traditional IVF procedures ( 1…

Figure 52. EGFR mutation status determines the…

Figure 52. EGFR mutation status determines the outcome of erlotinib as a therapy

Figure 53. EGFR mutation status must be…

Figure 53. EGFR mutation status must be determined in order to ensure that erlotinib is…

Figure 54. Potential therapeutic approaches for DMD

( A ) In healthy muscle the dystrophin…

Figure 55. The use of CRISPR/Cas9 in…

Figure 55. The use of CRISPR/Cas9 in DMD

In stem cells from the patient CRISPR/Cas9…

Figure 56. Cost per genome over time

As a comparison, expected fall in cost as…

Chromosome structure and chromosomal disorders

To learn more about general genetics, consult one of many available text books. The following is freely available online.
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The sex chromosomes, X and Y

Bonora G. and Disteche C.M. (2017) Structural aspects of the inactive X chromosome. Phil. Trans. R. Soc. B Biol. Sci. 372, 20160357, (and others in this volume of 12 contributions to a discussion meeting issue ‘X-chromsome inactivation: a tribute to Mary Lyon’) 10.1098/rstb.2016.0357 - DOI - PMC - PubMed
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Gilbert S.F. (2000) Developmental Biology, 6th edn, Chromosomal Sex Determination in Mammals Sinauer Associates
Lombardi L.M., Baker S.A. and Zoghbi H.Y. (2015) MECP2 disorders: from the clinic to mice and back. J. Clin. Invest. 125, 2914–2923 10.1172/JCI78167 - DOI - PMC - PubMed

Single-gene disorders

Chial H. (2008) Mendelian genetics: patterns of inheritance and single-gene disorders. Nat. Education 1, 63
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Mitochondrial disorders

Chinnery P. (2000) Mitochondrial Disorders Overview. SourceGeneReviews® (Adam M.P., Ardinger H.H., Pagon R.A., Wallace S.E., Bean L.J.H., Stephens K. and Amemiya A., eds), pp. 1993–2018, University of Washington, Seattle, Seattle (WA)
Chong J.X., Buckingham K.J., Jhangiani S.N., Boehm C., Sobreira N., Smith J.D.. et al. (2015) The genetic basis of mendelian phenotypes: discoveries, challenges, and opportunities. Am. J. Hum. Genet. 97, 199–215 10.1016/j.ajhg.2015.06.009 - DOI - PMC - PubMed
Nightingale H., Pfeffer G., Bargiela D., Horvath R. and Chinnery P. F. (2016) Emerging therapies for mitochondrial disorders. Brain 139, 1633–1648 10.1093/brain/aww081 - DOI - PMC - PubMed
Reznichenko A., Huyser C. and Pepper M. (2016) Mitochondrial transfer: implications for assisted reproductive technologies. Appl. Transl. Genom. 11, 40–47 10.1016/j.atg.2016.10.001 - DOI - PMC - PubMed

Epigenetics

Barlow D.P. and Bartolomei M.S. (2014) Genomic imprinting in mammals. Cold Spring Harb. Perspect. Biol. 6, a018382 10.1101/cshperspect.a018382 - DOI - PMC - PubMed
Lobo I. (2008) Genomic imprinting and patterns of disease inheritance. Nat. Education 1, 66
Schuebel K., Gitil M., Domschke K. and Goldman D. (2016) Making sense of epigenetics. Int. J. Neuropsychopharmacol. 19, 1–10 10.1093/ijnp/pyw058 - DOI - PMC - PubMed
Soshnev A.A., Josefowicz S.Z. and Allis C.D. (2016) Greater than the sum of parts: complexity of the dynamic epigenome. Mol. Cell 62, 681–694 10.1016/j.molcel.2016.05.004 - DOI - PMC - PubMed
Venturá-Junca P., Irarrázaval I., Rolle A.J., Gutiérrez J.I., Moreno R.D. and Santos M.J. (2015) In vitro fertilization (IVF) in mammals: epigenetic and developmental alterations. Scientific and bioethical implications for IVF in humans. Biol. Res. 48:, 68 10.1186/s40659-015-0059-y - DOI - PMC - PubMed

Complex disorders

Chial H. and Craig J. (2008) Genome-wide association studies (GWAS) and obesity. Nat. Education 1, 80
Prasad R.B. and Groop L. (2015) Genetics of type 2 diabetes–pitfalls and possibilities. Genes 6, 87–123 10.3390/genes6010087 - DOI - PMC - PubMed
Schulz L.C. (2010) The Dutch Hunger Winter and the developmental origins of health and disease. Proc. Natl. Acad. Sci. U.S.A. 107, 16757–16758 10.1073/pnas.1012911107 - DOI - PMC - PubMed

Cancer: mutation and epigenetics

Aunan J.R., Cho W.C. and Søreide K. (2017) The biology of aging and cancer: a brief overview of shared and divergent molecular hallmarks. Aging Dis. 8, 628–642 10.14336/AD.2017.0103 - DOI - PMC - PubMed
Burotto M., Chiou V.L., Lee J-M. and Kohn E.C. (2014) The MAPK pathway across different malignancies: A new perspective. Cancer 120, 3446–3456 10.1002/cncr.28864 - DOI - PMC - PubMed
Delbridge A.R., Valente L.J. and Strasser A. (2012) The role of the apoptotic machinery in tumor suppression. Cold Spring Harb. Perspect. Biol. 4, a008789. - PMC - PubMed
Feinberg A.P., Koldobskiy M.A. and Gondor A. (2016) Epigenetic modulators, modifiers and mediators in cancer aetiology and progression. Nat. Rev. Genet. 17, 284–299 10.1038/nrg.2016.13 - DOI - PMC - PubMed
Fischer M. and Müller G.A. (2017) Cell cycle transcription control: DREAM/MuvB and RB-E2F complexes. Crit. Rev. Biochem. Mol. Biol. 52, 638–662 10.1080/10409238.2017.1360836 - DOI - PubMed
Feero W.G. and Gutmacher A.E. (2014) Genomics, personalized medicine, and paediatrics. Acad. Pediatr. 14, 14–22 10.1016/j.acap.2013.06.008 - DOI - PMC - PubMed
Genomics England, 100,000 genomes project, 2018. https://www.genomicsengland.co.uk/
Naidoo N., Pawitan Y., Soong R., Cooper D.N. and Ku C.-S. (2011) Human genetics and genomics a decade after the release of the draft sequence of the human genome. Hum. Genomics 5, 577–622 10.1186/1479-7364-5-6-577 - DOI - PMC - PubMed
Rehm H.L. (2017) Evolving healthcare through personal genomics. Nat. Rev. Genet. 18, 259–267 10.1038/nrg.2016.162 - DOI - PMC - PubMed
Scottish Genomes Partnership (2018), https://www.scottishgenomespartnership.org/

Genetic testing in the diagnostic laboratory

Bishop R. (2010) Applications of fluorescence in situ hybridization (FISH) in detecting genetic aberrations of medical significance. Biosci. Horiz. 3, 85–95, 10.1093/biohorizons/hzq009 - DOI
Ferrie R.M., Schwarz M.J., Robertson N.H., Vaudin S., Super M., Malone G.. et al. (1992) Development, multiplexing, and applications of ARMS tests for common mutations in the CFTR gene. Am. J. Hum. Genet. 51, 251–262 - PMC - PubMed
Frese K.S., Katus H.A. and Meder B. (2013) Next-generation sequencing: from understanding biology to personalized medicine. Biology (Basel) 2, 378–398 - PMC - PubMed
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Diagnosis, management and therapy of genetic disease

Aronson S.J. and Rehm H.L. (2015) Building the foundation for genomics in precision medicine. Nature 526, 336–342 10.1038/nature15816 - DOI - PMC - PubMed
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Lockyer E. (2016) The potential of CRISPR-Cas9 for treating genetic disorders. Biosci. Horiz. 9, 10.1093/biohorizons/hzw012 - DOI
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Challenges in delivering a genetics service

Blashki G., Metcalfe S. and Emery J. (2014) Genetics in general practice. Aust. Fam. Phys. 43, 428–431 - PubMed
Harris A., Kelly S. E. and Wyatt S. (2013) Counseling customers: emerging roles for genetic counselors in the direct-to-consumer genetic testing market. J. Genet. Couns. 22, 277–288 10.1007/s10897-012-9548-0 - DOI - PMC - PubMed
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Ethical Issues in Genetic Testing

Committee Opinion CO
Number 410
June 2008

Informed Consent

Prenatal genetic testing, genetic data and the family, genetic data and insurers and employers, genetics and assisted reproductive technology, conclusions, recommendations.

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Number 410 (Reaffirmed 2020)

Committee on Ethics

Committee on Genetics

This document reflects emerging clinical and scientific advances as of the date issued and is subject to change. The information should not be construed as dictating an exclusive course of treatment or procedure to be followed.

ABSTRACT: Genetic testing is poised to play an increasing role in the practice of obstetrics and gynecology. To assure patients of the highest quality of care, physicians should become familiar with the currently available array of genetic tests and the tests’ limitations. Clinicians should be able to identify patients within their practices who are candidates for genetic testing. Candidates will include patients who are pregnant or considering pregnancy and are at risk for giving birth to affected children as well as gynecology patients who, for example, may have or be predisposed to certain types of cancer. The purpose of this Committee Opinion is to review some of the ethical issues related to genetic testing and provide guidelines for the appropriate use of genetic tests by obstetrician–gynecologists. Expert consultation and referral are likely to be needed when obstetrician–gynecologists are confronted with these issues.

Although ethical questions related to genetic testing have been recognized for some time, they have gained a greater urgency because of the rapid advances in the field as a result of the success of the Human Genome Project. That project—a 13-year multibillion-dollar program—was initiated in 1990 to identify all the estimated 20,000–25,000 genes and to make them accessible for further study. The project harnessed America’s scientists in a quest for rapid completion of a high-priority mission but left a series of ethical challenges in its wake. When developing the authorizing legislation for the federally funded Human Genome Project, Congress recognized that ethical conundrums would result from the project’s technical successes and included the need for the development of federally funded programs to address ethical, legal, and social issues. Accordingly, the U.S. Department of Energy and the National Institutes of Health earmarked portions of their budgets to examine the ethical, legal, and social issues surrounding the availability of genetic information.

The purpose of this Committee Opinion is to review some of the ethical issues related to genetic testing and provide guidelines for the appropriate use of genetic tests by obstetrician–gynecologists. It is important to note at the outset, given the increasing complexity of this field and the quickness with which it advances, that expert consultation and referral are likely to be needed when obstetrician–gynecologists are confronted with many of the issues detailed in this Committee Opinion.

The pace at which new information about genetic diseases is being developed and disseminated is astounding. Thus, the ethical obligations of clinicians start with the need to maintain competence in the face of this evolving science. Clinicians should be able to identify patients within their practices who are candidates for genetic testing. Candidates will include patients who are pregnant or considering pregnancy and are at risk for giving birth to affected children as well as gynecology patients who, for example, may have or be predisposed to certain types of cancer.

If a patient is being evaluated because of a diagnosis of cancer in a biologic relative and is found to have genetic susceptibility to cancer, she should be offered counseling and follow-up, with referral as appropriate, to ensure delivery of care consistent with current standards. In fact, genetic screening for any clinical purpose should be tied to the availability of intervention, including prenatal diagnosis, counseling, reproductive decision making, lifestyle changes, and enhanced phenotype screening.

One of the pillars of professionalism is social justice, which would oblige physicians to “promote justice in the health care system, including the fair distribution of health care resources” 1 . In the context of genetic testing, justice would require clinicians to press for resources, independent of an individual’s ability to pay, when they encounter barriers to health care for their patients who require care as a consequence of genetic testing and diagnosis 1 .

Obstetrician–gynecologists also are ideally positioned to educate women. When they, or experts in genetics to whom they refer, counsel on genetics, they should provide accurate information and, if needed, emotional support for patients burdened by the results or consequences of genetic diagnoses, be they related to preconception or prenatal care, cancer risks, or other implications for health. Finally, clinicians should familiarize their patients with steps that can be taken to mitigate health risks associated with their genetic circumstance (eg, having a colonoscopy if there is a predisposition to colon cancer) 2 .

It recently has been suggested that each person’s entire genome may be available for use by physicians for diagnostic and therapeutic purposes in the not-too-distant future 3 . Although that might seem like a medical panacea, the potential risks associated with wide-scale genetic testing are substantial. Many incidental findings will come to light, and yet, although those tested may be tempted to believe otherwise, genetic findings do not equate directly with either disease or health: “one hundred percent accurate identification of such incidental pathologies will lead to iatrogenic pathology… the belief that genetics completely determines phenotypic outcome must be informed by an understanding that most genetic measurements only shift the probability of an outcome, which often depends on other environmental triggers and chance” 4 .

Genetic Exceptionalism

Before the appropriate process for obtaining consent for genetic tests is considered, it is necessary to confront the broader question of whether the consequences of the results of those tests are substantively different from the consequences of other “medical” tests, for which specific consent is not always obtained. Some ethicists argue against what has been called the “exceptionalism” of genetic tests 5 . They maintain that many medical tests have consequences for patients that are similar to those of genetic tests. For example, there can be discrimination by insurance companies against individuals either with a genetic disease or with a disease that is not linked to any particular gene. Results of nongenetic tests, as well as genetic tests, can divulge information about family members (eg, tests for sexually transmitted diseases). Additionally, both genetic and nongenetic tests can provide information about a person’s medical future. As such, some authors have concluded that many genetic test results “may cause stigmatization, family discord and psychological distress. Regardless of whether a test is genetic, when this combination of characteristics is present…testing should be performed with particular caution and the highest standards of informed consent and privacy protection should be applied” 6 .

However, others argue that genetics should be treated as a unique class and be subject to a more rigorous process for consent. They base their belief on several factors. Genes, they argue, do not merely inform patients and their health care providers about the diagnosis of an extant illness. They also foretell the possibility (or in some cases the certainty) of a future disease, thus allowing “perfectly healthy” individuals to be subject to discrimination based on a predisposing gene. The DNA sample—which can be viewed as “a coded probabilistic medical record”— “makes genetic privacy unique and differentiates it from the privacy of medical records” 7 . Some believe that this information is even more sensitive given the uncertainties attached to genetic results (ie, the reliability of tests, the penetrance of genes, and the unavailability of efficacious interventions to reduce the consequences of genetic diseases). Additionally, the consequence of being found to carry a particular gene has resonance not only for the individual who is tested but also for family members.

Patients should be informed that genetic testing could reveal that they have, are at risk for, or are a carrier of a specific disease. The results of testing might have important consequences or require difficult choices regarding their current or future health, insurance coverage, career, marriage, or reproductive options.

Role of the Obstetrician–Gynecologist

In addition to needing to ensure proper consent, the obstetrician–gynecologist who orders genetic tests should be aware of when it is appropriate to test, which particular test to order, and “what information the test can provide, the limitations of the test, how to interpret positive and negative results in light of the patient’s medical or family history, and the medical management options available” 8 . The health care provider ordering tests has a responsibility to use and interpret those tests correctly or to refer to someone with relevant expertise. Because completing all these tasks is particularly difficult when direct-to-consumer marketing of genetic tests is used, that marketing approach has significant limitations 9 . These enterprises receive compensation only if an individual, after counseling, chooses to undergo a test, bringing the standard of neutral counseling into question and further rendering the use of a market-driven approach to testing ethically problematic 10 . In the end, the physician plays an important role in providing adequate, neutral counseling; ensuring informed consent; and providing follow-up for genetic tests. Neutral counseling also may be compromised through the use of patient educational materials or counselors that are provided by a company that might profit from a patient’s decision to undergo testing.

Particular caution should be exercised when obtaining consent for collecting genetic material that may be stored and, therefore, can have future clinical or research applications. The American College of Medical Genetics (ACMG) recommends that when samples are obtained for clinical tests, counseling should address the anticipated use of samples, including whether their use will be restricted for the purpose for which they were collected and if and when they will be destroyed 11 . When samples will be used for research or the development of diagnostic tests, the ACMG recommends that consent should include a description of the work (eg, its purposes, limitations, possible outcomes, and methods for communicating and maintaining confidentiality of results). There should be a discussion with the research participant about whether she wishes to give permission to use her samples without identifiers for other types of research, and she should be informed of the institution’s policy regarding recontacting participants in the future. Current and future use of samples for research should follow state and federal regulations governing protection of human participants in research 12 . Two authors recently suggested that the “best consumer advice, given current law, is that one should not send a DNA sample to anyone who does not guarantee to destroy it on completion of the specified test” 7 . Others argue for the creation of a repository of samples donated by genetic altruists to be used for many different types of research 4 .

Genetic Testing in Children and Adolescents

Testing of children presents unique issues in counseling and consent. Although it is most commonly pediatricians or geneticists who are called on to test children for genetic diseases, obstetricians may be asked to test already born children of parents who, through the process of prenatal testing, have been found to be carriers of genetic diseases. In such cases, the physician should balance the rights of the parents to have information that can optimize the ongoing health care of their children against the rights of the children to have their best interests protected. There will be circumstances in which it can be determined that a child is at risk for an untoward clinical event in the future, but there may be no information about interventions that have the potential to reduce the likelihood of that event or the magnitude of its effect. In that circumstance, the benefits of testing a child are not always clear (eg, BRCA testing in a young child).

Timely medical benefit to the child should be the primary justification for genetic testing in children and adolescents. If the medical benefits are uncertain or will be deferred to a later time, this justification for testing is less compelling.

If the medical or psychosocial benefits of a genetic test will not accrue until adulthood, as in the case of carrier status or adult-onset diseases, genetic testing generally should be deferred. Further consultation with other genetic services providers, pediatricians, psychologists, and ethics committees may be appropriate to evaluate these conditions.

Testing should be discouraged when the health care provider determines that potential harms of genetic testing in children and adolescents outweigh the potential benefits. A health care provider has no obligation to provide a medical service for a child or adolescent that is not in the best interest of the child or adolescent.

The ASHG and ACMG concluded, “Providers who receive requests for genetic testing in children must weigh the interests of children and those of their parents and families. The provider and the family both should consider the medical, psychosocial, and reproductive issues that bear on providing the best care for children” 8 .

Physicians (obstetricians and pediatricians) also have a responsibility to provide information to patients regarding newborn screening. The primacy of the child’s welfare should animate these discussions as well. More detail about this issue can be found elsewhere 14 .

Genetic testing of the fetus offers both opportunities and ethical challenges. Preconception and prenatal genetic screening and testing are recommended for a limited number of severe child-onset diseases because such screening and testing provides individuals with the chance to pursue assisted reproductive technology in order to avoid conception of an affected child, to consider termination of a pregnancy, or to prepare for the birth of a chronically ill child. With advancing genetic technology, however, physicians may increasingly face requests for testing of fetuses for less severe child-onset conditions, adult-onset conditions, or genetically linked traits.

Principles regarding testing of children provide some guidance for when prenatal testing might be appropriate but this decision is significantly complicated by the various purposes that prenatal testing can have: to detect a fetal condition for pregnancy termination, to allow patients to prepare for the birth and care of a potentially affected child, or, more rarely, to detect and treat a fetal condition in utero. Furthermore, many times, a woman’s intentions regarding pregnancy termination evolve as genetic information becomes available to her. Therefore, testing the fetus for adult-onset disorders with no known therapeutic or preventive treatment (save prevention by pregnancy termination) should raise caution in a way similar to the manner in which testing of children can. In pregnancies likely to be carried to term, consideration should be given to whether, as in the case of testing children, the decision to test should be reserved for the child to make upon reaching adulthood. However, consideration also should be given to personal preference, that is, the interests individuals may have in terminating a pregnancy that may result in a life (such as life that will be affected by Huntington chorea) that they feel morally obliged or prefer not to bring into the world. Because these often are wrenching decisions for parents, referral to parent support networks (eg, National Down Syndrome Society, if that is the diagnosis of concern), counselors, social workers, or clergy may provide additional information and support 15 .

In a large number of instances, when patients receive the results of genetic tests, they are party to information that directly concerns their biologic relatives as well. This familial quality of genetic information raises ethical quandaries for physicians, particularly related to their duty of confidentiality. In these circumstances, some have posited an ethical tension between obligations the clinician has to protect the confidentiality of the individual who has consented to a test on the one hand and a physician’s duty to protect the health of a different individual on the other hand. For example, a woman who discovers that she is a carrier of an X-linked recessive disease during the workup of an affected son might choose not to tell her pregnant sister about her carrier status because she does not believe in abortion and fears that her sister might consider an abortion 16 . In another example, a woman identified as a carrier of a gene predisposing individuals to cancer might not wish to share the information with relatives, some of whom might even be patients of the same physician who tested her, because such sharing would disclose her own status as a carrier.

In both the previously cited cases, information obtained with the consent of one individual could assist in the management of another. However, medical ethics as reflected in American Medical Association (AMA) policies recognizes a physician’s duty to safeguard patient confidences in such cases (with a few notable exceptions, often mandated by law—for example, communicable diseases and gunshot and knife wounds should be reported as required by applicable statutes or ordinances) 17 . How assiduously that confidentiality needs to be guarded is the subject of some debate. Some have argued that genetic information should be subject to stringent safeguards because, even though there may be uncertainty about the ultimate biologic consequence of a given gene, the social consequences (discrimination and stigmatization) can be substantial 18 . The AMA’s Council on Ethical and Judicial Affairs has argued that physicians do indeed have an obligation to pay almost unlimited obeisance to a patient’s confidentiality save only for “certain circumstances which are ethically and legally justified because of overriding social considerations” 19 .

Conversely, there are those who argue against the withholding of important information from potentially affected family members 20 . Those who subscribe to this belief feel that when information applies to family as much as to the proband, an obligation arises that extends from the physician to those potentially affected family members but no further. This view is consistent with court rulings in three states, which have held that a physician owes a duty to the patient’s potentially affected family members 21 22 23 24 . Two of these rulings addressed the question of how physicians must fulfill this duty and reached different conclusions. In one case, the court held that the physician can discharge the duty by informing the patient of the risk and is not required to inform the patient’s child 22 . In another case, the court did not decide how the physician could satisfy the duty to warn, other than requiring that “reasonable steps be taken to assure that the information reaches those likely to be affected or is made available for their benefit” 23 . As these alternate decisions illustrate, the legal limits of privacy are evolving, emphasizing the need for patient communication and case-by-case evaluation.

Recommendations of Other Organizations

Organizations that promulgate guidelines for genetic care and counseling also have proposed different approaches to the disclosure of genetic information. The ASHG tailors its recommendations to the magnitude and immediacy of risk faced by kindred 25 , encouraging voluntary disclosure by the proband but also articulating circumstances in which the proband’s refusal to do so should not preclude disclosure by the health care provider. According to the ASHG, disclosure is acceptable if “the harm is likely to occur, and is serious, immediate and foreseeable.” It adds that the at-risk relative must be identifiable and that there must be some extant intervention that can have a salutary effect on the course of the genetic disease. In summary, “the harm from failing to disclose should outweigh the risk from disclosure.” Although this suggestion to disclose seems unequivocal, it also posits circumstances for its exercise that are highly unlikely at the current time (ie, very few genetic diagnoses pose an immediate risk, let alone ones that can be substantively modified with an intervention 25 ).

The President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research also suggested circumstances in which a health care provider should disclose information in the absence of the proband’s permission to do so 26 . The commission indicated that disclosure is required when four conditions are present: 1) efforts to elicit voluntary disclosure by the proband have failed, 2) there is a high probability that harm will occur if disclosure is not made, and intervention can avert that harm, 3) the harm would be serious, and 4) efforts are made to limit disclosed information to genetic information needed for diagnosis and treatment. Although the commission did not cite a requirement for an immediate risk, the requirements for a high probability of harm and for the availability of an efficacious intervention make it likely that adherence to these guidelines rarely will result in cases in which a patient’s rights of confidentiality are overridden in order to inform relatives at risk.

The best way for the obstetrician–gynecologist to avoid the challenging choice between involuntary disclosure and being passive in the face of risks to kindred is to anticipate the issue and raise it at the first genetic counseling session. At that session, the patient needs to be educated about the implications of findings for relatives and why voluntary disclosure would in many circumstances be encouraged (as well as the possibility that relatives might prefer not to know the results). Some bioethicists have even suggested that these sessions should be used as an opportunity for clinicians to articulate the circumstances under which they would consider disclosure obligatory, thus allowing patients to seek care elsewhere if they found the conditions for testing unacceptable (Macklin has referred to this as the “genetic Miranda warning”) 27 . Similarly, even if the health care provider would not disclose without consent under any circumstance, the initial counseling session could allow the health care provider to refer the patient elsewhere if they find they have an irreconcilable difference or have an objection of conscience in expectations about disclosure. Physicians also should make themselves available to assist patients at the time of disclosure if that will help assuage their patients’ concerns.

A particularly thorny issue related to the ownership of genetic information might be results that bear on paternity. It is possible that prenatal assessments and family testing might reveal that the husband, partner, or other putative father is not the biologic father. In 1994, the Committee on Assessing Genetic Risks of the Institute of Medicine recommended that in such situations the health care provider should inform a woman but should not disclose this information to her partner 28 . The Institute of Medicine’s reason for withholding such information was that “genetic testing should not be used in ways that disrupt families.” Another reason may be that the physician–patient relationship exists solely with the woman. Others have disagreed with the Institute of Medicine’s recommendation 29 . In some cases, it is not merely a matter of acting to protect families. For example, suppose a child is born with a disease that is caused by an autosomal recessive gene, and the husband does not carry the deleterious gene because he is not actually the father. If the physician were to maintain the charade of paternity, then the counseling given to both parents (ie, there is one chance in four that each subsequent child will have the same disease) would be false and might lead the husband to argue against more children or for unnecessary amniocenteses in all future pregnancies, or inappropriately lead to concern for others in his family.

Other circumstances exist in which the interests of a pregnant woman and family members might diverge. For example, if the husband’s father has Huntington chorea (an autosomal dominant trait), the pregnant woman might wish to test the fetus for the gene. If the father did not want to know his own status, a conflict would arise, pitting her right to know about her fetus against his right not to know about himself. Another example of conflict would be if problems arose during diagnostic linkage studies for prenatal or preclinical diagnosis in a family and some family members did not want to participate in the testing (eg, testing for thalassemia). It might then be impossible to make a diagnosis in the index case. Both ethical and legal precedents, however, argue that individuals cannot be forced to have such testing.

Concerns about access to health and life insurance in the face of the discovery of a deleterious or predisposing gene is one of the most nettlesome issues facing health care providers who wish to use genetic testing to improve the health of their patients. In some ways, the importance of this issue is more pronounced in the United States because of the manner in which health care coverage is obtained. In countries with universal health care, individuals with the diagnosis of a predisposing gene need not fear the loss of access to health insurance.

In recognition of concerns related to genetic testing, in 1995, the Equal Employment Opportunity Commission issued guidelines stating that individuals who thought they had been discriminated against by an employer because of predictive genetic testing had the right to sue that employer. Additionally, the Health Insurance Portability and Accountability Act (HIPAA), enacted in 1996, prevented insurance companies from denying health care based on predictive testing for individuals transferring from one plan to another 30 . Physicians should advocate for patients’ ability to obtain health or life insurance uncompromised by the results of any genetic tests they might undergo.

Although there is scant evidence of widespread genetic discrimination, there is clear evidence that fear of that discrimination can drive patients away from needed testing or from participation in research and also may influence physicians’ uses of genetic tests 31 . In commenting on insurance and discrimination and considering needed protections and legislation, ACMG makes the following points: legislation must not impede the ability of individuals to maximize use of genetic information in their health care and employment decision making, and it must not limit the access of health care providers to genetic information needed to ensure that the care provided is beneficial and specific to the needs of the individual. Furthermore, the privacy of genetic information must be adequately protected. Protection against unfair discrimination on the basis of genetic risk for disease is achieved only by strategies that restrict use of genetic information in enrollment and rate-setting. Protected genetic information must include information based on evaluation, testing, and family histories of individuals and their family members 32 . Finally, as discussed before, it must be recognized that the confidentiality of these data has become difficult to guarantee in this era of electronic medical records.

There are at least two issues that relate to the intersection of genetics and assisted reproductive technology (ART). In the first instance, there is the need to consider whether all individuals, regardless of genotype, should have access to ART using their own gametes. In the past, individuals who were infected with deleterious viruses that have the potential to be passed to their children (eg, human immunodeficiency virus) were denied access to ART, in part because, before the advent of a variety of interventions, as many as one in four of their offspring would acquire an ultimately fatal infection, a risk similar to that if both parents are carriers for a serious autosomal recessive disease. Others have argued, however, that “procreative liberty should enjoy presumptive primacy when conflicts about its exercise arise because . . . [it] is central to personal identity, to dignity and to the meaning of one’s life” 33 . Such principles would support allowing prospective parents to be arbiters of the level of risk to which a child could be exposed.

Second is the question of the extent to which preimplantation genetics should be used in pursuit of the “genetically ideal” child. The American College of Obstetricians and Gynecologists (ACOG) already opposes all forms of sex selection not related to the diagnosis of sex-linked genetic conditions 34 . In the near future, other potentially controversial genetic manipulations may be available. Complex genetic systems such as cognition and aging soon may be determinable and may be constituents of potentially desirable characteristics, such as intelligence or longevity. They could, therefore, be used or misused as parameters for prenatal diagnosis 35 . Some have argued for a permissive approach, allowing parents to choose from a menu of possible children the one with the chance for the “best life.” That approach would allow selection for both disease-related genes (eg, eliminating carriers of BRCA genes) and nondisease genes “even if this maintains or increases social inequality” 36 . One author has referred to this as “procreative beneficence,” defining it as couples selecting, from the possible children they could have, the child who is expected to have the best life, or at least as good a life as the others, based on the relevant, available information 36 . Conversely, in the United Kingdom, strict limits are set on the use of prenatal genetic diagnosis, and clinics must apply for a license for every new disease they want to include in screening. However, even in that country, the list of allowable preimplantation genetic diagnosis tests has been expanded recently to include susceptibilities for certain cancers 37 38 .

Parents’ requests to select a certain genetic trait may pose even greater challenges for reproductive endocrinologists and embryologists when parents’ choices seem to be antithetical to the best interests of the future child. For example, deaf parents may prefer to select for an embryo that will yield a child who will also be deaf. Couples who have short stature due to skeletal dysplasia might feel they would prefer to have a child of similar stature. The technical ability to provide these choices is not far from reality, but the ethical roadmap that will offer direction to physicians is not as clearly laid out.

Genetic testing is poised to play a greater and greater role in the practice of obstetrics and gynecology. To assure patients of the highest quality of care, physicians should be familiar with the currently available array of genetic tests, as well as with their limitations. They also should be aware of the untoward consequences their patients might sustain because of a genetic diagnosis. The physician should work to minimize those consequences. Genetic information is unique in being shared by a family. Physicians should inform their patients of that fact and help them to prepare for dealing with their results, including considering disclosure to their biologic family. If the genetic information could potentially benefit family members (eg, allow them to improve their own prognosis), physicians should guide their patients toward voluntary disclosure while assiduously guarding their right to confidentiality.

Clinicians should be able to identify patients within their practices who are candidates for genetic testing and should maintain competence in the face of increasing genetic knowledge.

Obstetrician–gynecologists should recognize that geneticists and genetic counselors are an important part of the health care team and should consult with them and refer as needed.

Discussions with patients about the importance of genetic information for their kindred, as well as a recommendation that information be shared with potentially affected family members as appropriate, should be a standard part of genetic counseling.

Obstetrician–gynecologists should be aware that genetic information has the potential to lead to discrimination in the workplace and to affect an individual’s insurability adversely. In addition to including this information in counseling materials, physicians should recognize that their obligation to professionalism includes a mandate to prevent discrimination. Steps that physicians can take to fulfill this obligation could include, among others, advocacy for legislation to ban genetic discrimination.

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Copyright © June 2008 by the American College of Obstetricians and Gynecologists, 409 12th Street, SW, PO Box 96920, Washington, DC 20090-6920. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, posted on the Internet, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Requests for authorization to make photocopies should be directed to: Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400.

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Essay on Genetics (For College and Medical Students) | Biology

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Essay on Genetics

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ADVERTISEMENTS: (adsbygoogle = window.adsbygoogle || []).push({}); 1. Essay on the Meaning of Genes:

The term ‘gene’ was coined by Danish botanist Wilhelm Johannsen in 1909. It is the basic physical and functional unit of heredity. Heredity is the transfer of characters from parents to their offspring that is why children resemble their parents. A hereditary unit consists of a sequence of DNA (except in some viruses that contain RNA, instead) that occupies a specific location on a chromosome and determines a particular characteristic in an organism. DNA is a vast chemical information database that carries the complete set of instructions for making all the proteins that a cell will ever need.

Each gene contains a particular set of instructions, usually coding for a particular protein. Genes achieve their effects by directing protein synthesis. The sequence of nitrogenous bases along a strand of DNA determines the genetic code. When the product of a particular gene is needed, the portion of the DNA molecule that contains that gene splits, and a complementary strand of RNA, called messenger RNA (mRNA), forms and then passes to ribosomes, where proteins are synthesized.

A second type of RNA, transfer RNA (tRNA), matches up the mRNA with specific amino acids, which combine in series to form polypeptide chains, the building blocks of proteins. Experiments have shown that many of the genes within a cell are inactive much or even all of the time, but they can be switched on and off.

DNA resides in the core, or nucleus, of each of the body’s trillions of cells. Every human cell (with the exception of mature red blood cells, which have no nucleus) contains the same DNA. Each human cell has 46 molecules of double-stranded DNA. Human cells contain two sets of chromosomes, one set inherited from the mother and one from the father. (Mature sperm and egg cells carry a single set of chromosomes). Each set has 23 single chromosomes – 22 autosomes and an X or Y sex chromosome. (Females inherit an X from each parent, while males get an X from the mother and a Y from the father.) In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases.

The Human Genome Project has estimated that humans have between 20,000 and 25,000 genes. Every person has two copies of each gene, one inherited from each parent. Most genes are the same in all people, but a small number of genes (less than 1 percent of the total) are slightly different between people. Alleles are forms of the same gene with small differences in their sequence of DNA bases. These small differences contribute to each person’s unique physical features. Genes carry information that determines the traits, the characteristics we inherit from our parents. The branch of biology that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms is known as genetics.

2. Essay on Mendelian Genetics :

Sir Gregor Johann Mendel (1822 to 1884) was Austrian monk who used garden pea (Pisum sativum) for his experiments and published his results in 1865. His work, however, was rediscovered in 1900, long after Mendel’s death, by Tschermak, Correns and DeVries. Mendel was the first to suggest principles underlying inheritance. He is regarded as the founder or father of genetics. He developed the concept of the factors to explain results obtained while cross breeding strains of garden peas. He identified physical characteristics (phenotypes), such as plant height and seed colour, which could be passed on, unchanged, from one generation to another.

The hereditary factor that predicted the phenotype was later termed a “gene”. The genetic constitution of an organism is known as genotype. Mendel hypothesized that genes were inherited in pairs, one from the male and one from the female parent. Plants that bred true had inherited identical genes (homozygotes) from their parents, whereas plants that did not breed true inherited alternative copies (hybrids, or heterozygotes) of the genes (alleles) from one parent that were similar, but not identical, to those from the other parent.

Alleles are the alternative forms of the same gene which determine contrasting characters. One chromosome might contain a version of the eye colour gene that produces blue eyes, and other chromosome might contain a version that produces brown eyes. If an individual has both versions of the gene, the individual is heterozygous for the eye colour trait. If an individual has the same version of the eye colour gene on both chromosomes, the individual is homozygous for the eye colour trait. In case plants the allelic character of height are the tall (T) and dwarf (t).

Alleles are one alternative of a pair or group of genes that could occupy a specific position on a chromosome. Genes are composed of sequences of nucleotides, and a variation in this sequence can affect the protein made from that gene. A change in the manufacture of a protein in an organism often leads to an observable result. There are many different alleles for the gene that manufactures protein to give humans their unique eye colour. There are two alleles for flower colour in the common garden pea.

Some of these alleles had a greater effect on the phenotypes of hybrids than others. For example, if a single copy of a given allele was sufficient to produce the same phenotype seen in homozygous organisms, that gene is termed a “dominant”. Conversely, if the allele could only be detected in the minority of the offspring of hybrid parents that were homozygous for that “weaker” allele, the gene is termed a “recessive”. Dominant and recessive are relative terms. Consider a plant with a gene for red flower colour and a gene for blue flower colour.

This plant bears red flowers, although it has a gene for blue flower colour, too. Red flower colour is the dominant trait, while blue flower colour is the recessive trait. The red colour gene in a sense overpowers the blue colour gene. In order for the plant to have blue flowers, it would need to completely lack the gene for red flower colour. Dominant traits are normally represented by uppercase letters, such as R. The corresponding recessive trait would be represented by a lowercase letter, r. A plant with genotype Rr will have red flowers, as would a plant with genotype RR. But a plant with genotype rr would have blue flowers.

Mendelian genetics, also known as classical genetics, is the study of the transmission of inherited characteristics from parent to offspring. Gregor Mendel actually calculated the ratios of observable characteristics in the common garden pea plant Pisum sativum. Mendel studied seven characteristics in peas including seed texture, seed colour, flower colour, flower position; stem length, pod shape and pod colour (Fig. 6.1). Peas were a good model system, because he could easily control their fertilization by transferring pollen with a small paintbrush.

This pollen could come from the same flower (self-fertilization), or it could come from another plant’s flowers (cross-fertilization). Because the seven pea plant characteristics tracked by Mendel were consistent in generation after generation of self- fertilization. These parental lines of peas could be considered pure-breeders (or, in modern terminology, homozygous for the traits of interest). Mendel and his assistants eventually developed 22 varieties of pea plants with combinations of these consistent characteristics. He applied mathematics and statistics to analyze the results obtained by him.

Mendel started his pea breeding program by allowing certain pea plants to repeatedly self-fertilize. Peas are able to fertilize their own flowers which are called selfing. If pea selfing continues over many generations the pea plants will be homozygous or have an identical pair of genes for a certain characteristic. These plants will contain either two identical recessive genes (homozygous recessive) for a characteristic or two identical dominant genes (homozygous dominant) for the same characteristic and are considered pure-breeding for those characteristics.

For example, purple flower colour in peas is dominant and white flower colour in peas is recessive. When a white flowered (homozygous recessive) pea plant is crossed with a purple flowered (homozygous dominant) pea plant, the resulting offspring all has purple flower colour.

The gene composition (genotype) for the flower genes in each of these types of pea plants is represented as shown below:

Mendel used characteristics of pea plants and four o’clock flowers (Mirabilis jalapa) to analyze the hereditary patterns of these traits. His historic experiments led him to the conclusion that inherited characteristics were carried in discrete, independent units (later named genes). In Mendel’s interpretation, hereditary characteristics occurred in pairs of factors that had specific relationships. Mendel first crossbred one tall, true-breeding plant with one short, true-breeding plant.

Contrary to the blending theory, all the offspring were tall. In terms of genotype, the original tall plant was TT (two dominant alleles; homozygous), the short plant was tt (two recessive alleles; homozygous), and the second-generation plants were Tt (one dominant and one recessive allele; heterozygous). When Mendel next allowed these plants to self-fertilize, he found that the short trait reappeared in the third generation. The ratio of short to tall plants was almost exactly 3:1. Their genotypes were as follows -1 short (tt) : 2 tall (Tt): 1 tall (TT). Based on these observations (Fig. 6.2), Mendel formulated a series of laws that are the basis of what we now term “Mendelian” inheritance patterns.

ADVERTISEMENTS: (adsbygoogle = window.adsbygoogle || []).push({}); 3. Essay on the Punnett Square :

Mendel worked by observing characteristics (phenotypes) and calculating the ratios of each type to form his principles of inheritance. However we can predict the ratios of phenotypes by using Mendel’s principles. One of the most common methods of determining the possible outcome of a cross between two parents is called a Punnett square. To perform a Punnett square one must first figure out all the possible combinations of the alleles to be studied for each parent.

The possible gametes for one parent go on the X axis and the possible gametes for the other parent go on the Y axis (one allele in each cell of the upper row (traditionally the mother) and rightmost column (traditionally the father). The gamete combinations are then paired in the squares below and to the side of each type, i.e. the offspring’s genotypes are then calculated by observing the intersection of the mother’s and father’s individual alleles (much like a multiplication table).

Eye colour in human is much more complex. A mother and father, both having the brown eye phenotype, have a child. We know that both parents carry the gene for blue eye colour and therefore are heterozygous for this trait. These parents can either donate a dominant B to the gamete or a recessive b to the gamete (Fig.6.3).

The outcome of this cross shows that 3 times out of 4 (75%) the child will have brown eyes and 1 out of 4 times the child will have blue eyes (25%). The probability that the child’s genotype will be heterozygous, for eye colour alleles, is 50%. The probability is 25% for either the homozygous recessive or dominant genotype.

X-linked characteristic: colour blindness in human

There are several known X-linked characteristics in humans but few, if any, Y-linked characteristics are usually reported. Females have two X chromosomes with one or the other X chromosome remaining active in a mosaic pattern in a tissue. Males have only one X chromosome so if the X chromosome of a male has a defective allele there is no companion X chromosome to compensate for the deficiency. A female must have the same defective allele on both her X chromosomes to demonstrate any deficiencies (Fig. 6.4).

4. Essay on the Mendelian Principles :

During Mendel’s time DNA had not been identified as the substance of heredity and it was unknown how offspring obtained certain characteristics from their parents. Since Mendel’s work elucidated dominant and recessive characteristics his study supported the particulate theory of inheritance. Mendel accomplished this work by calculating the ratios of observable characteristics of the offspring from known parental types.

The first parental types were homozygous recessive and homozygous dominant pure breeding types. The parental generation or P generation, by definition, is always homozygous recessive and homozygous dominant for the traits to be studied. The offspring which results from the mating of parental types (P generation) will always be heterozygous for the characteristic.

a. Mendel’s Law of Dominance:

The first law of Mendel states that “In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the progeny, in other words factors retain their identity from generation to generation and do not blend in the hybrid”. In other words it says that, if two plants that differ in just one trait are crossed, then the resulting hybrids will be uniform in the chosen trait. Depending on the traits is the uniform features either one of the parents’ traits (a dominant-recessive pair of characteristics) or it is intermediate.

When two pure breeding organisms of contrasting characters are crossed, only one character of the pair appears in the F1 generation, known as the dominant character (example- tallness) and the other unexpressed or hidden character is known as the recessive character (example- dwarfness). When Mendel crossed a true breeding red flowered plant with a true breeding white flowered one, the progeny was found to be red coloured. The white colour suppressed and the red colour dominated.

Mendel’s law of dominance is generally true, but there are many exceptions to the law. For each of the seven pairs of characters examined, it was observed that one allelomorph dominated over the other, so that F1 exhibits one or the other alternative phenotypes represented in the parents. Some inherited traits do not exhibit strict Mendelian dominant/ recessive relationships. The simplest example of this phenomenon is called codominance, or incomplete dominance.

This pattern is displayed in the colours of four o’clock flowers. When a white and a red flower are cross-fertilized, the second generation is all pink. However, when a pink flower is allowed to self-fertilize, the white and red attributes return. The colour ratios for this third-generation cross are – 1 white: 2 pink: 1 red. This pattern is due to the fact that three alleles, instead of the usual two, determine colour in four o’clock flowers. If red colour is designated R and white colour r, then pink colour (not red or white) is the phenotypic effect of genotype Rr. (This is one type of pattern formerly used in support of the blending theory of inheritance). Thus in certain cases the hybrid offsprings resemble one parent much more closely than the other but does not resemble it exactly, so the dominance is incomplete. This is termed as incomplete dominance (Fig. 6.5).

Another example of codominance is the ABO blood typing system used to determine the type of human blood. It is common knowledge that a blood transfusion can only take place between two people who have compatible types of blood. Human blood is separated into different classifications on the basis of presence and absence of specific antigens or proteins in the red blood cells.

The protein’s structure is controlled by three alleles; i, IA and IB. The first allele is, i, the recessive of the three, and IA and IB are both co-dominant when paired together. If the recessive allele i is paired with IB or IA, its expression is hidden and is not shown. When the IB and IA are together in a pair, both proteins A and B are present and expressed.

The ABO system is called a multiple allele system for there are more than two possible allele pairs for the locus. The individual’s blood type is determined by which combination of alleles he/she has. There are four possible blood types in order from most common to most rare- O, A, B and AB. The O blood type represents an individual who is homozygous recessive (ii) and does not have an allele for A or B (Table 6.2).

Blood types A and B are co-dominant alleles. Co-dominant alleles are expressed even if only one is present. The recessive allele i for blood type O is only expressed when two recessive alleles are present. Blood type O is not apparent if the individual has an allele for A or B. Individuals who have blood type A have a genotype of IAIA or IAi and those with blood type B, IBIB or IBi, but an individual who is IAIB has blood type AB.

b. Mendel’s Law of Segregation:

The law of segregations is a law of inheritance proposed by Mendel in 1866. According to this law, “each organism is formed of a bundle of characters. Each character is controlled by a pair of factors (genes). During gamete formation, the two factors of a character separate and enter different gametes”. This law is also called law of purity of gametes. At formation of gametes, the two chromosomes of each pair separate (segregate) into two different cell which form the gametes.

This is a universal law and always during gamete formation in all sexually reproducing organisms, the two factors of a pair pass into different gametes. Each gamete receives one member of a pair of factors and the gametes are pure. That is two members (alleles) of a single pair of genes are never found in the same mature sperm or ovum (gamete) but always separate out (segregate).The factors of inheritance (genes) normally are paired, but are separated or segregated in the formation of gametes (eggs and sperm), i.e., it states that the individuals of the F 2 generation are not uniform, but that the traits segregate.

Depending on a dominant-recessive crossing or an intermediate crossing are the resulting ratios 3:1 or 1:2:1. This concept of independent traits explains how a trait can persist from generation to generation without blending with other traits. It explains, too, how the trait can seemingly disappear and then reappear in a later generation. The principle of segregation was consequently of the utmost importance for understanding both genetics and evolution.

Monohybrid Cross:

The crossing of two plants differing in one character is called monohybrid cross. Mendel carried out monohybrid experiments on pea plants and based on the results of monohybrid experiment, he formulated the law of segregation. Mendel selected two pea plants, one with a tall stem and the other with a dwarf or short stem. These plants were considered as parental plants (P) and were pure breed. A pure plant is one that breeds true in respect of a particular character for a number of generations. The pure-bred tall and dwarf plants were treated as parents and were crossed.

Seeds were collected from these plants. These seeds were sown and a group of plants were raised. These plants constituted the first filial generation (F1 generation). All the F1 plants were tall and were inbred. The seeds were collected and the next generation (F2) was raised. In the F2 generation, two types of plants were found. They were tall and dwarf. Mendel counted the number of tall and dwarf plants. Of the 1064 plants of F2 generation, 787 plants were tall and 277 plants were dwarf (75% were tall plants and 25% were dwarf plants). Thus the tall plants occurred in the ratio 3: 1 (Fig. 6.6).

c. Mendel’s Principle of Independent Assortment:

The Principle of Independent Assortment describes how different genes independently separate from one another when reproductive cells develop. Mendel formulated the Principle of Independent Assortment from the observations he got from the dihybrid crosses, which are crosses between organisms that differ with regard to two traits.

It is now known that this independent assortment of genes occurs during meiosis in eukaryotes. Meiosis is a type of cell division that reduces the number of chromosomes in a parent cell by half to produce four reproductive cells called gametes. In humans, diploid cells contain 46 chromosomes, with 23 chromosomes inherited from the mother, while a second similar set of 23 chromosomes inherited from the father. Pairs of similar chromosomes are called homologous chromosomes. During meiosis, the pairs of homologous chromosome are divided in half to form haploid cells, and this separation, or assortment of homologous chromosomes is random. This means that all the maternal chromosomes will not be separated into one cell, while all the paternal chromosomes are separated into another. Instead, after meiosis occurs, each haploid cell contains a mixture of genes from the organism’s mother and father.

Another feature of independent assortment is recombination. Recombination occurs during meiosis and is a process that breaks and recombines the pieces of DNA to produce new combinations of genes. Recombination scrambles pieces of maternal and paternal genes, which ensures that genes assort independently from one another. It is important to note that there is an exception to the law of independent assortment for genes that are located very close to one another on the same chromosome because of genetic linkage.

Dihybrids Cross between Two Heterozygous Individuals:

A dihybrid cross is a breeding experiment between P generation (parental generation) organisms that differ in two traits. Mendel determined what happens when two plants that are each hybrid for two traits are crossed. Mendel therefore decided to examine the inheritance of two characteristics at once. Based on the concept of segregation, he predicted that traits must sort into gametes separately. By extrapolating from his earlier data, Mendel also predicted that the inheritance of one characteristic did not affect the inheritance of a different characteristic.

Mendel tested the idea of trait independence with more complex crosses. First, he generated plants that were pure bred for two characteristics, such as seed colour (yellow and green) and seed shape (round and wrinkled). These plants would serve as the Pi generation for the experiment. In this case, Mendel crossed the plants with Round and Yellow seeds (RRYY) with plants with wrinkled and green seeds (rryy). From his earlier monohybrid crosses, Mendel knew which traits were dominant- round and yellow.

So, in the F 1 generation, he expected all round, yellow seeds from crossing these pure bred varieties, and that is exactly what he observed. Mendel knew that each of the Fi progeny were dihybrids; in other words, they contained both alleles for each characteristic (RrYy). He then crossed individual Fi plants (with genotypes RrYy) with one another. This is called a dihybrid cross. Mendel’s results from this cross were present in a 9:3:3:1 ratio. The outcome shows a phenotypic ratio of 9 of the offspring having yellow round peas, 3 having yellow wrinkled peas, 3 having green round peas and 1 having green wrinkled peas. This is a classic 9:3:3:1 phenotypic ratio which is always the result in a dihybrid cross between two heterozygotes with unlinked traits.

The proportion of each trait was still approximately 3:1 for both seed shape and seed colour. In other words, the resulting seed shape and seed colour looked as if they had come from two parallel monohybrid crosses; even though two characteristics were involved in one cross, these traits behaved as though they had segregated independently. From these data, Mendel developed the third principle of inheritance- the principle of independent assortment i.e. alleles at one locus segregate into gametes independently of alleles at other loci. Such gametes are formed in equal frequencies (Fig. 6.7).

Trihybrid Cross:

A trihybrid cross is a breeding experiment between P generation (parental generation) organisms that differ in three traits (Fig. 6.8).

5. Essay on the Test Cross :

A test cross is a way to explore the genotype, the genetic makeup of an organism. Early use of the test cross was as an experimental mating test used to determine what alleles are present in the genotype. Consequently, a test cross can help to determine whether a dominant phenotype is homozygous or heterozygous for a specific allele.

Diploid organisms, like humans, have two alleles at each genetic locus, or position, and one allele is inherited from each parent. Different alleles do not always produce equal outward effects or phenotypes. One allele can be dominant and mask the effect of a second recessive allele in a heterozygous organism that carries two different alleles at a specific locus. Recessive alleles only express their phenotype if an organism carries two identical copies of the recessive allele, meaning it is homozygous for the recessive allele. This means that the genotype of an organism with a dominant phenotype may be either homozygous or heterozygous for the dominant allele. Therefore, it is impossible to identify the genotype of an organism with a dominant trait by visually examining its phenotype.

A test cross is the means by which a scientist can determine whether an individual with a dominant phenotype has a homozygous (AA) or heterozygous (Aa) dominant genotype. The test cross involves mating the individual with the dominant phenotype to an individual with a recessive (aa) phenotype and observing the offspring produced. If the individual being tested is homozygous dominant, then all offspring will have a dominant phenotype, since all the offspring will have at least one A (dominant) allele.

7. Essay on the Limitations of Mendelian System :

The simple system of Mendelian genetics is very powerful and serves to explain the inheritance patterns of numerous traits. However, many traits are controlled by many genes acting in tandem, and thus do not obey strict Mendelian patterns (although their constituent genes may). Furthermore, many human traits are strongly influenced by the environment as well, and therefore their phenotypes cannot be said to be Mendelian (though the genetic components may be). In sum, Mendelian patterns are important, but cannot be applied universally. Individual traits must be researched to find out if they obey typical Mendelian patterns.

8. Essay on the Polygenic or Quantitative Inheritance :

When a trait (feature or character) is controlled by a single gene it is termed monogenic inheritance. Many traits or features are controlled by a number of different genes. For example, the skin colour of humans and the kernel colour of wheat results from the combined effect of several genes, none of which are singly dominant. Polygenes affecting a particular trait are found on many chromosomes. Each of these genes has equal contribution and cumulative the total effect. Three to four genes contribute towards formation of the pigment in the skin of humans.

So there is a continuous variation in skin colour from very fair to very dark. Such inheritance controlled by many genes is termed quantitative inheritance or polygenic (poly meaning due many genes) inheritance. In polygenic inheritance, each dominant gene controls equally the intensity of the character. The effect of the dominant genes in cumulative and the intensity of character or trait depend upon the number of dominant genes (Fig. 6.10).

9. Essay on Multiple Alleles:

Alleles are located in corresponding parts of homologous chromosomes, only one member of a pair can be present in a given chromosome and only two are present in a cell of a diploid. Alleles are genes that are members of the same gene pair, each kind of allele affecting a trait differently than the other. A diploid organism has, by its definition, only two alleles at one time, yet exceptions to the rules do appear. Many examples were found where more than two alternative alleles, also called multiple alleles, are present.

In these cases two or more different mutations must have taken place at the same locus but in different individuals or at different times. Multiple alleles are alternative states at the same locus. The different alleles of a series are usually represented by the same symbol. Subscripts and superscripts are used to identify different members of a series of alleles. Most alleles produce variations of the same trait, but some produce very different phenotypes.

The most famous example of multiple alleles was discovered in rabbits. It was known that Albino rabbits were produced on occasion in variously coloured rabbit populations. After conducting a monohybrid cross between a coloured and Albino rabbit, it was discovered that the members of a pair of alternative genes, either c a or C, must be responsible for coloured or albino rabbits. A cross of homozygous coloured (CC) and albino (c a c a ) rabbits were made and the F1 generation was all coloured, while the F2 generation had three coloured and one albino. This showed that one pair of alleles was involved, the wild C and the mutant allele c a . It was determined that C was dominant over c a (Fig. 6.11).

Figure 6.11: Inheritance of skin colour

10. Essay on the Chromosomal Theory of Inheritance :

Sutton and Boveri in 1902 observed by that maternal (from mother) and paternal (from father) character come together in the progeny which is diploid or2n and has chromosomes in pairs and later on segregate during the formation of gametes. The gametes have a single chromosome from each pair and are haploid or n. Chromosomes from two parents come together in the same zygote as a result of the fusion of two gametes and again separate out during the formation of gametes. Chromosomes are filamentous bodies present in the nucleus and seen only during cell division. The above two observations proved that there is a remarkable similarity between the behavior of character during inheritance and that of chromosomes during meiosis.

This led Sutton and Boveri to propose ‘chromosomal theory of inheritance’ and its salient features are as follows:

a. The somatic (body) cells of an organism, which are derived by the repeated division of zygote have two identical sets of chromosomes, i.e., they are diploid. Out of these, one set of chromosomes is received from the mother (maternal chromosomes) and one set from the father (paternal chromosomes). Two chromosomes of one type (carrying same genes) constitute a homologous pair. Humans have 23 pairs of chromosomes.

b. The chromosomes of homologous pair separate out during meiosis at the time of gamete formation.

c. The behavior of chromosomes during meiosis indicates that Mendelian factors or genes are located linearly on the chromosomes. With progress in molecular biology it is now known that a chromosome is made up of a molecule of DNA and segments of DNA are the genes.

Essay on Sex-Linked Characteristics :

In animals the sex is determined by the presence or absence of the Y chromosome. The X and Y chromosomes are not homologous but are completely different chromosomes which carry unique information. No human can exist without at least one X chromosome. There is a viable human phenotype that has one X chromosome and no companion X or Y. These individuals are said to have the Turner syndrome. Turner syndrome (X 0) individuals are females who are of normal to above intelligence and usually have few deficiencies considering their lack of an entire chromosome. One major deficiency of Turner syndrome is sterility and non-development of secondary sexual characteristics.

Certain traits in humans and other organisms can demonstrate sex-linked inheritance of characteristics. This means that the inherited traits are present on the sex determining chromosomes the X or the Y. Since there appears to be more information on the X chromosome than on the Y chromosome of humans, most known sex-linked characteristics are actually X- linked characteristics.

In sex-linked traits, such as colour-blindness, the gene for the trait is found on the X chromosome (a sex chromosome). Sex-linked traits affect primarily males, since they have only one copy of the X chromosome (male genotype: XY). Females, who have two copies of the X chromosome, are affected only if they are homozygous for the trait. Females can, however, be carriers for sex-linked traits, passing their X chromosomes on to their sons. Sex-linked inheritance works as follows- if a female carrier and a normal male give birth to a daughter, she has a 1 in 2 chance of being a carrier of the trait (like her mother). If the child is a son, he has a 1 in 2 chance of being affected by the trait. If a female carrier and an affected male give birth to a daughter, she will either be affected or be a carrier. If the child is a son, he will either be affected or be entirely free of the gene.

Another example of a sex-linked trait is haemophilia, made famous by the “Queen Victoria pedigree” of the European nobility. Beginning with Queen Victoria of England (in whom it was probably a spontaneous mutation), the haemophilia gene spread quickly throughout the European rulers (who intermarried as a matter of course). The disease, which prevents blood from clotting properly and renders a minor injury a life-threatening event, claimed several young men of the royal line. Especially since male heirs were preferred over female as successors to the thrones of Europe, the spread of such a debilitating disease was a major problem.

11. Essay on the Linkage and Crossing Over :

The fact behind Mendel’s success was the genes encoding his selected traits did not reside close together on the same chromosome. If they had, his dihybrid cross results would have been much more confusing, and he might not have discovered the law of independent assortment. The law of independent assortment holds true as long as two different genes are on separate chromosomes. When the genes are on separate chromosomes, the two alleles of one gene (A and a) will segregate into gametes independently of the two alleles of the other gene (B and b). Equal numbers of four different gametes will result- AB, aB, Ab, ab. But if the two genes are on the same chromosome, then they will be linked and will segregate together during meiosis, producing only two kinds of gametes.

For instance, if the genes for seed shape and seed colour were on the same chromosome and a homozygous double dominant (yellow and round, RRYY) plant was crossed with a homozygous double recessive (green and wrinkled, rryy), the F 1 hybrid offspring, as usual, would be double heterozygous dominant (yellow and round, RrYy). However, since in this example the R and Y are linked together on the chromosome inherited from the dominant parent, with r and y linked together on the other chromosome, only two different gametes can be formed- RY and ry.

Therefore, instead of 16 different genotypes in the F 2 offspring, only three are possible: RRYY, RrYy, rryy and instead of four different phenotypes, only the original two will exist. Notice that the inheritance pattern now resembles that seen in a monohybrid cross, with a 3:1 phenotypic ratio, rather than the 9:3:3:1 ratio expected from the dihybrid cross. If physically linked on a single chromosome, the round and yellow alleles would segregate together, and the wrinkled and green alleles would segregate together, no round green seeds or wrinkled yellow seeds would ever appear.

The above explanation, however, neglects the influence of the crossing over of genetic material that occurs during meiosis. The farther away two genes are from one another, the more likely an exchange point for crossing over will form between them. At these exchange points, the alleles of one gene switch to the opposite homologous chromosome, while the other gene alleles remain with their original chromosomes. When alleles switch places like this, the resulting gametes are called recombinant. In the example above, the original parental gametes would be RY and ry, while the recombinant gametes would be Ry and rY. Thus four different kinds of gametes will be formed, instead of only two formed when the genes were linked (Fig. 6.12).

If two genes are extremely close together, crossing over will almost never occur between them, and the recombinant gametes will almost never form. If they are very far apart on the chromosome, crossing over will almost certainly occur between them, and recombinant gametes will form just as often as if the genes were on different chromosomes (50 percent of recombinant). If the genes are at an intermediate distance from each other, crossing over may sometimes occur between them and sometimes not (Fig. 6.13).

Therefore, the percentage of recombinant gametes (reflected in the percentage of recombinant offspring) correlates with the distance between two genes on a chromosome. By comparing the recombination rates of multiple different pairs of genes on the same chromosome, the relative position of each gene along the chromosome can be determined. This method of ordering genes on a chromosome is called a linkage map.

12. Essay on Mutations:

Mutations are errors in the genotype that create new alleles and can result in a variety of genetic disorders. In order for a mutation to be inherited from one generation to another, it must occur in sex cells, such as eggs and sperm, rather than in somatic cells. The best way to detect a genetic disorder is karyotyping.

i. Autosomal Mutations :

There are certain human genetic diseases which are inherited in a Mendelian fashion such as disease phenotype will have either a clearly dominant or clearly recessive pattern of inheritance, similar to the traits in Mendel’s peas. Such a pattern will usually only occur if the disease is caused by an abnormality in a single gene. The mutations that cause these diseases occur in genes on the autosomal chromosomes, the chromosomes that determine bodily characteristics and exist in all cells, both sex and somatic, as opposed to sex-linked diseases.

ii. Recessive Disorders :

Genetic disorders are initially arises as a new mutation that changes a single gene so that it no longer produces a protein that functions normally. A disease resulting from a mutation that an allele which produces a non-functional protein will be inherited in a recessive fashion so that the disease phenotype will only appear when both copies of the gene carry the mutation, resulting in a total absence of the necessary protein. If only one copy of the mutated allele is present, the individual is a heterozygous carrier, showing no signs of the disease but able to transmit the disease gene to the next generation.

Albinism is an example of a recessive illness, resulting from a mutation in a gene that normally encodes a protein needed for pigment production in the skin and eyes. Many recessive illnesses occur with much greater frequency in particular racial or ethnic groups that have a history of intermarrying within their own community. For example, Tay-Sachs disease is especially common among people of Eastern European Jewish descent. Other well-known autosomal recessive disorders include sickle-cell anaemia and cystic fibrosis.

iii. Dominant Disorders :

Usually, a dominant phenotype results from the presence of at least one normal allele producing a protein that functions normally. In the case of a dominant genetic illness, there is a mutation that results in the production of a protein with an abnormal and harmful action. Only one copy of such an allele is needed to produce disease, because the presence of the normal allele and protein cannot prevent the harmful action of the mutant protein. Huntington’s disease, which killed folksinger Woody Guthrie, is a dominant genetic illness. A single mutant allele produces an abnormal version of the Huntington protein; this abnormal protein accumulates in particular regions of the brain and gradually kills the brain cells.

iv. Chromosomal Disorders :

Mutation of a single gene results in recessive and dominant characteristics. Some genetic disorders result from the gain or loss of an entire chromosome. Normally, paired homologous chromosomes separate from each other during the first division of meiosis. If one pair fails to separate, an event called non-disjunction, then one daughter cell will receive both chromosomes and the other daughter cell will receive none. When one of these gametes joins with a normal gamete from the other parent, the resulting offspring will have either one or three copies of the affected chromosome, rather than the usual two.

(a) Trisomy:

A single chromosome contains hundreds to thousands of genes. A zygote with three copies of a chromosome (trisomy), instead of the usual two, generally cannot survive embryonic development. Chromosome 21 is a major exception to this rule; individuals with three copies of this small chromosome (trisomy 21) develop the genetic disorder called Down syndrome. People with Down syndrome show at least mild mental disabilities and have unusual physical features including a flat face, large tongue, and distinctive creases on their palms. They are also at a much greater risk for various health problems such as heart defects and early Alzheimer’s disease.

(b) Monosomy:

The absence of one copy of a chromosome (monosomy) causes even more problems than the presence of an extra copy. Only monosomy of the X chromosome is compatible with life.

Polyploidy occurs when a failure occurs during the formation of the gametes during meiosis. The gametes produced in this instance are diploid rather than haploid. If fertilization occurs with these gametes, the offspring receive an entire extra set of chromosomes. In humans, polyploidy is always fatal, though in many plants and fish it is not.

Mendel’s Law of Inheritance | Genetics
Laws of Heredity by Mendel | Genetics

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Nursing Ethics of Genetic Testing and Research Essay

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Introduction

For nurses and other healthcare workers, including genetic testing and research, there are a number of ethical issues to consider. The prospect of genetic discrimination, respect for autonomy, confidentiality, voluntary participation, and secrecy are among these factors. It is crucial for nurses to comprehend these ethical questions and ensure they are properly handled in clinical settings. Informed compliance is one of the most significant ethical challenges in genetic testing and research.

Before delving further into these practices, nurses must ensure that patients completely comprehend the implications of genetic testing, as well as the potential dangers and advantages. (Uveges & Dwyer, 2022). Privacy and secrecy are two more serious ethical concerns in genetic testing and research. Nurses have a responsibility to ensure that patient genetic information is kept private and not disseminated without the patient’s informed permission. Genetic information must be used with extreme caution for research purposes, and strong regulations must be in place to protect patient privacy.

Genetic discrimination is another critical challenge in genetic testing and study. A nurse must accept their duty for ensuring that patients understand the hazards of genetic discrimination and are aware of their legal rights to protect themselves from discrimination. Nurses must also campaign for regulations that prevent genetic discrimination. Furthermore, nurses have a crucial function in assisting patients and families who have received genetic test results. This includes assisting them in understanding and interpreting the results as well as giving emotional support (Uveges & Dwyer, 2022). Nurses must also ensure that patients have access to genetic counseling services that are appropriate for them.

In conclusion, genetic testing and research in Canada create a number of ethical issues for nurses. We must be aware of these problems in order to defend patients’ rights in all stages.

Uveges, M. K., & Dwyer, A. A. (2022). Genetics: Nurses Roles and Responsibilities . The International Library of Bioethics , 153–174. Web.

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213 Genetics Research Topics & Essay Questions for College and High School

Genetics studies how genes and traits pass from generation to generation. It has practical applications in many areas, such as genetic engineering, gene therapy, gene editing, and genetic testing. If you’re looking for exciting genetics topics for presentation, you’re at the right place! Here are genetics research paper topics and ideas for different assignments.

🧬 TOP 7 Genetics Topics for Presentation 2024

🏆 best genetics essay topics, ❓ genetics research questions, 👍 good genetics research topics & essay examples, 🌟 cool genetics topics for presentation, 🌶️ hot genetics topics to write about, 🔎 current genetic research topics, 🎓 most interesting genetics topics.

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Aspects of the Genetic Diseases Genetic diseases are disorders that happen through mutations that occur in the human body. They can be monogenic, multifactorial, and chromosomal.
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Nutrition: Obesity Pandemic and Genetic Code The environment in which we access the food we consume has changed. Unhealthy foods are cheaper, and there is no motivation to eat healthily.
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Does Genetic Predisposition Affect Learning in Other Disciplines? This paper aims to examine each person’s ability to study a discipline for which there is no genetic ability and to understand how effective it is.
How Much Do Genetics Affect Us?
What Can Livestock Breeders Learn From Conservation Genetics and Vice Versa?
How Do Genetics Affect Caffeine Tolerance?
How Dolly Sheep Changed Genetics Forever?
What Is the Nature and Function of Genetics?
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How Does Genetics Affect the Achievement of Food Security?
Are Owls and Larks Different in Genetics When It Comes to Aggression?
How Do Neuroscience and Behavioral Genetics Improve Psychiatric Assessment?
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What Are Three Common Genetics Disorders?
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Why Tampering With Our Genetics Will Be Beneficial?
How Genetics and Environment Affect a Child’s Behaviors?
Which Country Is Best for Genetics Studies?
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Can Crop Models Identify Critical Gaps in Genetics, Environment, and Management Interactions?
How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?
Can You Change Your Genetics?
How Old Are European Genetics?
Will Benchtop Sequencers Resolve the Sequencing Trade-off in Plant Genetics?
What Can You Study in Genetics?
What Are Some Genetic Issues?
Does Genetics Matter for Disease-Related Stigma?
How Did the Drosophila Melanogaster Impact Genetics?
What Is a Genetics Specialist?
Will Genetics Destroy Sports?
Detection of Genetically Modified Products Today, people are becoming more concerned about the need to protect themselves from the effects of harmful factors and to buy quality food.
Genetically Modified Organisms Solution to Global Hunger It is time for the nations to work together and solve the great challenge of feeding the population by producing sufficient food and using fewer inputs.
Genetic Engineering: Cloning With Pet-28A Embedding genes into plasmid vectors is an integral part of molecular cloning as part of genetic engineering. An example is the cloning of the pectate lyase gene.
Researching of Genetic Engineering DNA technology entails the sequencing, evaluation and cut-and-paste of DNA. The following paper analyzes the historical developments, techniques, applications, and controversies.
Genetically Modified Crops: Impact on Human Health The aim of this paper is to provide some information about genetically modified crops as well as highlight the negative impacts of genetically modified soybeans on human health.
Genetic Engineering Biomedical Ethics Perspectives Diverse perspectives ensure vivisection, bio, and genetic engineering activities, trying to deduce their significance in evolution, medicine, and society.
Down Syndrome: The Genetic Disorder Down syndrome is the result of a glandular or chemical disbalance in the mother at the time of gestation and of nothing else whatsoever.
Genetic Modifications: Advantages and Disadvantages Genetic modifications of fruits and vegetables played an important role in the improvement process of crops and their disease resistance, yields, eating quality and shelf life.
Genetics of Personality Disorders The genetics of different psychological disorders can vary immensely; for example, the genetic architecture of schizophrenia is quite perplexing and complex.
Labeling of Genetically Modified Products Regardless of the reasoning behind the labeling issue, it is ethical and good to label the food as obtained from genetically modified ingredients for the sake of the consumers.
Convergent Evolution, Genetics and Related Structures This paper discusses the concept of convergent evolution and related structures. Convergent evolution describes the emergence of analogous or similar traits in different species.
Genetic Technologies in the Healthcare One area where genetic technology using DNA works for the benefit of society is medicine, as it will improve the treatment and management of genetic diseases.
Are Genetically Modified Organisms Really That Bad? Almost any food can be genetically modified: meat, fruits, vegetables, etc. Many people argue that consuming products, which have GMOs may cause severe health issues.
Type 1 Diabetes in Children: Genetic and Environmental Factors The prevalence rate of type 1 diabetes in children raises the question of the role of genetic and environmental factors in the increasing cases of this illness.
Discussion of Genetic Testing Aspects The primary aim of the adoption process is to ensure that the children move into a safe and loving environment.
Ethical Concerns on Genetic Engineering The paper discusses Clustered Regularly Interspaced Short Palindromic Repeats technology. It is a biological system for modifying DNA.
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Medicine Is Not a Genetic Supermarket Together with the development of society, medicine also develops, but some people are not ready to accept everything that science creates.
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Genetic Modification of Organisms to Meet Human Needs Genetic modification of plants and animals for food has increased crop yields as the modified plants and animals have more desirable features such as better production.
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Genetic Testing and Bill of Rights and Responsibilities Comparing the Patient Bill of Rights or Patient Rights and Responsibilities of UNMC and the Nebraska Methodist, I find that the latter is much broader.
Genetically Modified Products: Positive and Negative Sides This paper considers GMOs a positive trend in human development due to their innovativeness and helpfulness in many areas of life, even though GMOs are fatal for many insects.
Overview of African Americans’ Genetic Diseases African Americans are more likely to suffer from certain diseases than white Americans, according to numerous studies.
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Genetically Modified Fish: The Threats and Benefits This article’s purpose is to evaluate possible harm and advantages of genetically modified fish. For example, the GM fish can increase farms’ yield.
DNA and the Birth of Molecular Genetics Molecular genetics is critical in studying traits that are passed through generations. The paper analyzes the role of DNA to provide an ample understanding of molecular genetics.
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Genetically Modified Foods: How Safe are they? This paper seeks to address the question of whether genetically modified plants meant for food production confer a threat to human health and the environment.
The Genetic Material Sequencing This experiment is aimed at understanding the real mechanism involved in genetic material sequencing through nucleic acid hybridization.
Genetically Modified Organisms in Human Food This article focuses on Genetically Modified Organisms as they are used to produce human food in the contemporary world.
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Human Genome and Application of Genetic Variations Human genome refers to the information contained in human genes. The Human Genome Project (HGP) focused on understanding genomic information stored in the human DNA.
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The molecular mechanisms of aging and longevity.
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The effects of genes on athletic performance.
CRISPR-Cas9 gene editing: current applications and future perspectives.
Genetic underpinnings of human intelligence.
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Genetic ancestry testing: the process and importance.
Ban on Genetically Modified Foods Genetically modified (GM) foods are those that are produced with the help of genetic engineering. Such foods are created from organisms with changed DNA.
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Neurobiology: Epigenetics in Cocaine Addiction Studies have shown that the addiction process is the interplay of many factors that result in structural modifications of neuronal pathways.
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Darwin’s Theory of Evolution: Impact of Genetics New research proved that genetics are the driving force of evolution which causes the revision of some of Darwin’s discoveries.
Case on Preserving Genetic Mutations in IVF In the case, a couple of a man and women want to be referred to an infertility specialist to have a procedure of in vitro fertilization (IVF).
Race: Genetic or Social Construction One of the most challenging questions the community faces today is the following: whether races were created by nature or society or not.
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DNA Profiling: Genetic Variation in DNA Sequences The paper aims to determine the importance of genetic variation in sequences in DNA profiling using specific techniques.
Genetics: Gaucher Disease Type 1 The Gaucher disease type 1 category is a genetically related complication in which there is an automatic recession in the way lysosomes store some important gene enzymes.
Genetic Science Learning Center This paper shall seek to present an analysis of sorts of the website Learn Genetics by the University of Utah.
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Research of Genetic Disorders Types This essay describes different genetic disorders such as hemophilia, turner syndrome and sickle cell disease (SCD).
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Advantages of Using Genetically Modified Foods Genetic modifications of traditional crops have allowed the expansion of agricultural land in areas with adverse conditions.
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Personality Is Inherited Principles of Genetics The present articles discusses the principles of genetics, and how is human temperament and personality formed.
Literature Review: Acceptability of Genetic Engineering The risks and benefits of genetic engineering must be objectively evaluated so that modern community could have a better understanding of this problem
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The Effects of Genetic Modification of Agricultural Products Discussion of the threat to the health of the global population of genetically modified food in the works of Such authors as Jane Brody and David Ehrenfeld.
Genetic Engineering in Food and Freshwater Issues The technology of bioengineered foods, genetically modified, genetically engineered, or transgenic crops, will be an essential element in meeting the challenging population needs.
Genetic Engineering and Religion: Designer Babies The current Pope has opposed any scientific procedure, including genetic engineering, in vitro fertilization, and diagnostic tests to see if babies have disabilities.
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All About the Role of Genetic Engineering and Biopiracy The argument whether genetically engineered seeds have monopolized the market in place of the contemporary seeds has been going on for some time now.
Genetic Engineering and Cloning Controversy Genetic engineering and cloning are the most controversial issues in modern science. The benefits of cloning are the possibility to treat incurable diseases and increase longevity.
Biotechnology: Methodology in Basic Genetics The material illustrates the possibilities of ecological genetics, the development of eco-genetical models, based on the usage of species linked by food chain as consumers and producers.
Genetics Impact on Health Care in the Aging Population This paper briefly assesses the impact that genetics and genomics can have on health care costs and services for geriatric patients.
Genetic foundations of rare diseases.
Genetic risk factors for neurodegenerative disorders.
Inherited cancer genes and their impact on tumor development.
Genetic variability in drug metabolism and its consequences.
The role of genetic and environmental factors in disease development.
Genomic cancer medicine: therapies based on tumor DNA sequencing.
Non-invasive prenatal testing: benefits and challenges.
Genetic basis of addiction.
The origins of domestication genes in animals.
How can genetics affect a person’s injury susceptibility?
Concerns Regarding Genetically Modified Food It is evident that genetically modified food and crops are potentially harmful. Both humans and the environment are affected by consequences as a result of their introduction.
Family Genetic History and Planning for Future Wellness The patient has a family genetic history of cardiac arrhythmia, allergy, and obesity. These diseases might lead to heart attacks, destroy the cartilage and tissue around the joint.
Personal Genetics and Risks of Diseases Concerning genetics, biographical information includes data such as ethnicity. Some diseases are more frequent in specific populations as compared to others.
Genetic Predisposition to Alcohol Dependence and Alcohol-Related Diseases The subject of genetics in alcohol dependence deserves additional research in order to provide accurate results.
Genetically-Modified Fruits, Pesticides, or Biocontrol? The main criticism of GMO foods is the lack of complete control and understanding behind GMO processes in relation to human consumption and long-term effects on human DNA.
Genetic Variants Influencing Effectiveness of Exercise Training Programmes “Genetic Variants Influencing Effectiveness of Exercise Training Programmes” studies the influence of most common genetic markers that indicate a predisposition towards obesity.
Eugenics, Human Genetics and Their Societal Impact Ever since the discovery of DNA and the ability to manipulate it, genetics research has remained one of the most controversial scientific topics of the 21st century.
Genetic Interference in Caenorhabditis Elegans The researchers found out that the double-stranded RNA’s impact was not only the cells, it was also on the offspring of the infected animals.
Genetics and Autism Development Autism is associated with a person’s genetic makeup. This paper gives a detailed analysis of this condition and the role of genetics in its development.
Start Up Company: Genetically Modified Foods in China The aim of establishing the start up company is to develop the scientific idea of increasing food production using scientific methods.
Community Health Status: Development, Gender, Genetics Stage of development, gender and genetics appear to be the chief factors that influence the health status of the community.
Genetics of Developmental Disabilities The aim of the essay is to explore the genetic causes of DDs, especially dyslexia, and the effectiveness of DNA modification in the treatment of these disorders.
Homosexuality as a Genetic Characteristic The debate about whether homosexuality is an inherent or social parameter can be deemed as one of the most thoroughly discussed issues in the contemporary society.
Autism Spectrum Disorder in Twins: Genetics Study Autism spectrum disorder is a behavioral condition caused by genetic and environmental factors. Twin studies have been used to explain the hereditary nature of this condition.
Why Is the Concept of Epigenetics so Fascinating? Epigenetics has come forward to play a significant role in the modern vision of the origin of illnesses and methods of their treatment, which results in proving to be fascinating.
Epigenetics and Its Effect on Physical and Mental Health This paper reviews a research article and two videos on epigenetics to developing an understanding of the phenomenon and how it affects individuals’ physical and mental health.
Genomics, Genetics, and Nursing Involvement The terms genomics and genetics refer to the study of genetic material. In many cases, the words are erroneously used interchangeably.
Genetic Counseling for Cystic Fibrosis Some of the inherited genes may predispose individuals to specific health conditions like cystic fibrosis, among other inheritable diseases.
Genetic and Genomic Healthcare: Nurses Ethical Issues Genomic medicine is one of the most significant ways of tailoring healthcare at a personal level. This paper will explore nursing ethics concerning genetic information.
Patent on Genetic Discoveries and Supreme Court Decision Supreme Court did not recognize the eligibility of patenting Myriad Genetics discoveries due to the natural existence of the phenomenon.
Genetic Testing, Its Background and Policy Issues This paper will explore the societal impacts of genetic research and its perceptions in mass media, providing argumentation for support and opposition to the topic.
Genetically Modified Organisms and Future Farming There are many debates about benefits and limitations of GMOs, but so far, scientists fail to prove that the advantages of these organisms are more numerous than the disadvantages.
GMO: Some Peculiarities and Associated Concerns Genetically modified organisms are created through the insertion of genes of other species into their genetic codes.
Mitosis, Meiosis, and Genetic Variation According to Mendel’s law of independent assortment, alleles for different characteristics are passed independently from each other.
Genetic Counseling and Hypertension Risks This paper dwells upon the peculiarities of genetic counseling provided to people who are at risk of developing hypertension.
The Perspectives of Genetic Engineering in Various Fields Genetic engineering can be discussed as having such potential benefits for the mankind as improvement of agricultural processes, environmental protection, resolution of the food problem.
Labeling Food With Genetically Modified Organisms The wide public has been concerned about the issue of whether food products with genetically modified organisms should be labeled since the beginning of arguments on implications.
Diabetes Genetic Risks in Diagnostics The introduction of the generic risks score in the diagnosis of diabetes has a high potential for use in the correct classification based on a particular type of diabetes.
Residence and Genetic Predisposition to Diseases The study on the genetic predisposition of people to certain diseases based on their residence places emphasizes the influence of heredity.
Eugenics, Human Genetics and Public Policy Debates Ethical issues associated with human genetics and eugenics have been recently brought to public attention, resulting in the creation of peculiar public policy.
Genetics Seminar: The Importance of Dna Roles DNA has to be stable. In general, its stability becomes possible due to a large number of hydrogen bonds which make DNA strands more stable.
Genetically Modified Organisms: Position Against Genetically modified organisms are organisms that are created after combining DNAs of different species to come up with a transgenic organism.
Genetically Modified Organisms and Their Benefits Scientists believe GMOs can feed everyone in the world. This can be achieved if governments embrace the use of this new technology to create genetically modified foods.
Food Science and Technology of Genetic Modification Genetically modified foods have elicited different reactions all over the world with some countries banning its use while others like the United States allowing its consumption.
How Much can We Control Our Genetics, at What Point do We Cease to be Human? The branch of biology that deals with variation, heredity, and their transmission in both animals and the plant is called genetics.
Genetic Engineering: Gene Therapy The purpose of the present study is to discover just what benefits gene therapy might have to offer present and future generations.
Genetically Modified Foods and Their Impact on Human Health Genetically modified food has become the subject of discussion. There are numerous benefits and risks tied to consumption of genetically modified foods.
The Potential Benefits of Genetic Engineering Genetic engineering is a new step in the development of the humans’ knowledge about the nature that has a lot of advantages for people in spite of its controversial character.
Genetic Engineering: Dangers and Opportunities Genetic engineering can be defined as: “An artificial modification of the genetic code of an organism. It changes radically the physical nature of the being in question.

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J Gen Fam Med
v.21(3); 2020 May

Ethical considerations of gene editing and genetic selection

Jodie rothschild.

1 Rothschild Biomedical Communications, Seattle WA, USA

For thousands of years, humans have felt the need to understand the world around them—and ultimately manipulate it to best serve their needs. There are always ethical questions to address, especially when the manipulation involves the human genome. There is currently an urgent need to actively pursue those conversations as commercial gene sequencing and editing technologies have become more accessible and affordable. This paper explores the ethical considerations of gene editing (specifically germline) and genetic selection—including the hurdles researchers will face in trying to develop new technologies into viable therapeutic options.

1. BACKGROUND

1.1. gene editing.

Artificial manipulation of genes is a relatively new science, and a number of watershed moments have provided the foundation for the current state of genetic engineering. Researchers first discovered that nonspecific alterations to Drosophila DNA could be introduced using radiation 1 and chemicals 2 in 1927 and 1947, respectively. Greater understanding of the structure of the DNA molecule (such as the work of Watson, Crick, and Franklin, leading to the discovery of DNA’s double‐helix structure 3 ) and the cellular processes that govern its transcription, translation, replication, and repair (such as the function of ligases 4 and restriction enzymes 5 ) led to the first splicing experiments 6 and, ultimately, the first recombinant DNA 7 in the early 1970s. DNA recombination techniques were used extensively in the budding yeast Saccharomyces cerevisiae 8 , 9 beginning in the early 1980s, allowing researchers to study functional eukaryotic genomics. And in a significant advancement, the development of polymerase chain reaction (PCR) allowed scientists to amplify DNA, producing millions of copies from a single strand. 10

Around the same time, a number of laboratories created the first transgenic mice, 11 and about five years later, the first knockout mice were created. 12 Targeted gene editing was further advanced by the discovery that engineered endonucleases could create site‐specific double‐stranded breaks (DSBs), which in turn induce homologous recombination (HR), 13 , 15 the most common type of homology‐directed repair (HDR). When the Human Genome Project was declared complete in 2003, 15 it became possible to identify (and thus, theoretically, target) any human gene of interest.

The three main techniques for gene editing involve molecules that recognize and bind to specific DNA sequences; researchers can use custom molecules to affect genetic and epigenetic changes on essentially any gene. For example, these molecules can be combined with endonucleases, creating DSBs which can be repaired using either nonhomologous end joining (NHEJ), which often results in small random indel mutations, or HDR, which, when donor DNA with homology to either side of the cleavage site is present, can be used to create new or “repaired” versions of a target gene. The site‐specific DNA recognition molecule can also be combined with an effector molecule to up‐ or downregulate gene expression.

1.1.1. ZFPs/ZFNs

In the late 1970s and early 1980s, there was a large focus on understanding transcription factor IIIA (TFIIIA), the first eukaryotic transcription factor to be described. In 1983, researchers determined that zinc is required for TFIIIA function, 16 and in 1985 came the discovery that the zinc‐binding portions of the proteins are actually repeating motifs, independently folded to create finger‐like domains that grip the DNA. 17 This class of proteins is now referred to as zinc finger proteins (ZFPs), and several similar proteins have been discovered in the proteomes of a number of different organisms. Because each zinc finger recognizes three base pairs, 18 , 19 , 20 a peptide can be created to recognize a target gene by joining the appropriate zinc fingers in a linear fashion.

A 1994 paper describes a ZFP that was engineered to recognize and suppress an oncogene, as well as a ZFP that acted (in a different cell system) as a promoter of another gene by recognizing its activation domain. 21 The same paper suggests that ZFPs can be bound to effector proteins as a means of controlling gene expression.

Building on this idea, researchers fused a ZFP to the nonspecific cleavage domain of the Fok1 restriction enzyme. 22 The resulting heterodimer, known as a zinc finger nuclease (ZFN), can recognize a specific DNA sequence and produce a targeted DSB. As previously mentioned, these DSB can either be repaired via NHEJ, resulting in small indels, or HDR, which can be harnessed to insert an alternate or repaired gene. Fok1 must dimerize, so ZFNs must be created in pairs (one targeting the 3’ strand and the other targeting the 5’ strand) which improves target specificity—though efficiency remains relatively low (G‐rich sequences are especially difficult to target).

Ex vivo and in vivo delivery of ZFNs is relatively easy given their small size and the small size of the ZFN cassettes (which allows for the use of a variety of vectors). However, while ZFNs were certainly novel at the time they were developed, they are incredibly difficult and expensive to engineer, making them less practical in general than newer technologies.

1.1.2. TALEs/TALENs

In 2009, two different laboratories described a newly identified DNA‐binding motif: the transcription activator‐like effector (TALE), a protein secreted by the plant pathogen Xanthomonas . 23 , 24 Each TALE includes a DNA‐binding region composed of tandem repeats with repeat‐variable diresidues (RVDs) at positions 12 and 13; each RVD recognizes an individual nucleotide.

Like ZFPs, synthetic TALEs can be designed to affect gene regulation, 25 combined with effector proteins, or fused to endonucleases 26 , 27 , 28 to create TALE nucleases (TALENs); as with ZFNs, because Fok1 is the endonuclease used, TALENs must be created in pairs.

TALE nucleases are much larger than ZFNs, and so can be more difficult to deliver efficiently (especially in vivo). However, for myriad reasons (including the nature of their relative interactions with the DNA and the fact that each RVD recognizes a single base), TALE‐based chimeras (especially TALENs) can be built with higher specificity and greater targeting capacity than ZFP‐based chimeras. In addition, TALENs can be produced significantly more cheaply, easily, and with greater efficiency than ZFNs.

1.1.3. CRISPR‐Cas

In 1987, a laboratory in Osaka accidentally discovered an unusual palindromic repeat sequence in the E. coli genome they were studying, unique in that it was regularly interspaced. 29 These DNA motifs were further identified in various bacterial genomes by multiple laboratories over the next 20 years; their function, however, was still unknown. By 2005, three groups had independently determined that the spacer sequences were actually derived from phage DNA, 30 , 31 , 32 and the possibility of the genes playing a role in bacterial immunity was first suggested. 30 , 33 By this time, the scientific community referred to this unusual array as clustered regularly interspaced short palindromic repeats, or CRISPR. Meanwhile, researchers in the Netherlands had identified several other genes located near the CRISPR locus that appeared to be functionally associated with the CRISPR genes; 34 these would turn out to be the CRISPR associated proteins (Cas) that make up an integral part of the CRISPR‐Cas system.

In 2007, the CRISPR‐Cas system was identified as being a prokaryotic defense against pathogens. 35 As a part of a self‐/non–self‐determination mechanism of adaptive immunity, prokaryotes integrate a segment (generally 32‐38 base pairs) of phage DNA into their own genome, creating the spacers in the CRISPR arrays. After the CRISPR genes are transcribed, endoribonucleases cleave the resulting CRISPR RNA (pre‐crRNA), resulting in shorter RNA units composed of a single spacer sequence and the palindromic repeat (crRNA); depending on the organism, a trans‐activating crRNA (tracrRNA) may also be transcribed. The RNA forms a ribonucleoprotein (RNP) complex with the associated Cas proteins; any phage DNA containing the spacer sequence will be identified by the guiding RNA and cleaved by the endonuclease function of the Cas protein(s). The protospacer is the homologous sequence in the invading DNA, and is followed by a short protospacer adjacent motif (PAM); because the PAM is not incorporated in the CRISPR array, the CRISPR‐Cas complex is able to recognize the foreign DNA as non‐self (and thus will not cleave the prokaryotic cell's own DNA). 36

In 2012, Jennifer Doudna, Emmanuelle Charpentier, and others on their team engineered a synthetic chimera of the tracrRNA and crRNA (now known as single guide RNA, or sgRNA), which was able to direct Cas9 to create a targeted, site‐specific double‐stranded break. 37 By 2013, investigators had established that the CRISPR‐Cas9 was an effective, facile, and multiplexable method of editing the human genome. 38 , 39 , 40 , 41

Newer CRISPR‐based editing methods do not reply on unpredictable NHEJ or donor DNA. For example, endonuclease‐deficient Cas proteins can be fused to base‐editing enzymes; 42 first described in 2016, researchers have recently reported a high‐fidelity base editor with no off‐target mutations (OTMs). 43 Epigenetic techniques are also being explored using CRISPR‐Cas technology, 44 , 45 including linking endonuclease‐deficient Cas proteins to effector molecules. And prime editing addresses genetic disorders caused by multibase variances (such as sickle‐cell and Tay‐Sachs); in this case, the impaired Cas9 is fused to an engineered reverse transcriptase. 46

ZFNs and TALENs do maintain some advantages: CRISPR requires a PAM sequence, and sgRNA spacer sequences are usually only about 20 base pairs, meaning an inherently reduced targeting capacity (though researchers have recently begun exploring the effects of increased sgRNA length on cleavage efficiency and target specificity 47 ). CRISPR vectors are also necessary larger, making delivery more difficult. Overall, however, CRISPR is generally the preferred method of genetic and epigenetic manipulation, especially as improvements are made to the technology. CRISPR’s main advantage over its predecessors lies in the fact that rather than a complex protein as the DNA recognition molecule, the CRISPR system relies on a guide RNA. CRISPR kits are thus significantly cheaper, easier, and more efficiently produced than either ZFNs or TALENs.

1.2. Gene selection

Genetic selection happens in nature—natural selection is the mechanism that drives Darwinian evolution. Humans have also been practicing artificial selection for thousands of years, selecting for phenotypic traits when breeding plants and animals. New technologies have been developed over the last 53 years that allow selection of an embryo based on various criteria such as sex, ploidy, and polymorphisms.

1.2.1. Preimplantation genetic testing

Preimplantation genetic testing (PGT) encompasses various techniques used to screen embryos prior to transfer. Originally all referred to as preimplantation genetic diagnosis (PGD), there are actually three types of PGT: aneuploidy detection, now called PGT‐A; monogenic disorder detection, now called PGT‐M; and structural rearrangement detection, now called PGT‐SR.

Preimplantation genetic testing was ideated eleven years before the birth of the first in vitro fertilization (IVF) baby in 1978. Rabbit blastocysts were stained and observed using a fluorescence microscope; screening for sex chromatin allowed for the identification of the female embryos. 48 Because of the mutagenic potential of the preparation, the embryos were not implanted; a year later, cells from the trophoblasts of rabbit blastocysts were stained and sorted for sex, and the biopsied embryos transferred and allowed to grow to full term (at which point sex was confirmed). 49

Researchers then began to explore various methods of extracting a single embryonic cell for PGT: a blastomere biopsy (BB) removed during cleavage stage, 50 trophectoderm biopsy (TB), 51 and polar body biopsy. 52 Meanwhile, polymerase chain reaction (PCR) was developed in 1985 and quickly recognized as a potential tool for PGT when it was used to amplify the portion of the β‐globin locus that includes the Dde I site (absence of which is diagnostic for sickle‐cell anemia). 53 The blastomere biopsy technique and PCR were brought together in 1990 when two human pregnancies were established using sex selected embryos to eliminate the risk of inheriting recessive x‐linked conditions. 54

Fluorescence in situ hybridization (FISH) was the first cytogenetic technique to be used for PGT. Fluorochrome‐labeled site‐specific probes were hybridized to sample DNA, revealing aneuploidy and translocations; in 1993, two laboratories used FISH to identify X‐chromosomes, Y‐chromosomes, and aneuploidy. 55 , 56 However, the technique was limited by the number of chromosomes that could be assessed and by its inability to detect monogenic disorders.

Researchers then turned to comparative genomic hybridization (CGH) in 1999. 57 , 58 CGH can be thought of as competitive FISH: Sample and reference DNA are each labeled with a different color fluorophore, denatured, and allowed to hybridize to a metaphase spread. The DNA is then microscopically analyzed for differences in fluorescence intensity, indicating copy‐number variation (CNV).

While it was a vast improvement over its predecessor, CGH was time‐consuming (requiring embryos to be freeze‐thawed), labor‐intensive, and limited in its sensitivity. The next generation of CGH technology, array CGH (aCGH), addressed these limitations. 59 Like traditional CGH, aCGH allows for 24‐chromosome analysis; however, rather than human observation, fluorescence intensity evaluation is performed by a computer, locus by locus, with high specificity and resolution.

A number of other cytogenetic techniques for comprehensive chromosome screening (CCS) have since been developed: digital PCR (or dPCR, wherein a sample‐containing PCR solution is separated into tens of thousands of droplets and the reaction occurs separately in each partition), which can detect CNV, aneuploidy, mutations, and rare sequences; quantitative real‐time PCR (qPCR), in which a preamplification step prior to real‐time PCR allows for rapid detection of aneuploidy in all 24 chromosomes; single nucleotide polymorphism (SNP) array (which involves hybridizing fluorescent nucleotide probes to sample DNA and comparing the resulting fluorescence to a bioinformatic reference), which can detect imbalanced translocation, aneuploidy, and monogenic (and some multifactorial) disease; and next‐generation sequencing (NGS), the high‐throughput, massively parallel DNA sequencing technologies that allow for significantly quicker and cheaper sequencing than the Sanger method and make it possible to screen for everything from SNPs to aneuploidy.

Researchers and IVF laboratories use different combinations of FISH and/or the various CCS techniques.

1.2.2. Other prenatal testing

Often, IVF is not feasible, necessitating postimplantation prenatal testing (when indicated by family history and other risk factors). Amniocentesis, chorionic villus sampling (CVS), and percutaneous umbilical cord sampling (PUBS) were initially paired with karyotyping, which can detect sex, aneuploidy, and some types of structural chromosomal disorders. Karyotyping was superseded by chromosomal microarray techniques (aCGH and SNP array) and, more recently, low‐pass genome sequencing, as these technologies allow detection of CNVs as well as aneuploidy. 60

Amniocentesis is a procedure in which an ultrasound‐guided needle is inserted transabdominally in order to aspirate amniotic fluid. Applications of amniocentesis extend beyond genetic testing, such as assessment of fetal lung maturity, detection of Rh incompatibility, and decompression of polyhydramnios (accumulation of amniotic fluids).

Prior to 15 weeks’ gestation, the prenatal testing method of choice is CVS, a technique that involves analysis of samples taken from placental tissue. The CVS procedure is ultrasound‐guided and can be performed either transabdominally or transcervically (associated with higher miscarriage rates). CVS carries the risks of miscarriage, amniotic fluid leakage, and limb reduction defects and is limited by the possibility of placental mosaicism and maternal cell contamination.

Percutaneous umbilical cord sampling is a rarely used procedure, performed between 24 and 32 weeks’ gestation, in which fetal blood from the umbilical cord is obtained. Because of the high potential for complications, PUBS is generally reserved for cases in which the pregnancy is deemed high‐risk for genetic disorders and other testing methods (amniocentesis, CVS, and ultrasound) are unable to provide the needed information or have been inconclusive. PUBS is also used to provide more information about fetal health (such as blood gas levels and infection).

In 1997, the presence of cell‐free fetal DNA (cffDNA) in maternal blood was established using PCR amplification with Y‐chromosome probes. 61 This led to the development of noninvasive prenatal testing (NIPT) of cffDNA. NIPT has been shown to be an accurate and sensitive technique for the detection of some aneuploidies (such as trisomy 21 62 ), less so for others. 63 Because cffDNA comes from the placenta, placental mosaicism can result in inaccurate results. Further, NIPT detects all cell‐free DNA in the mother's blood, including her own; maternal mosaicism or malignancies can also contribute to inaccuracies. As such, NIPT is considered a screening test, rather than a diagnostic test.

2. ETHICS OF GENE EDITING

On November 25, 2018, news broke that Jiankui He of Southern University of Science and Technology in Shenzhen, China had registered a clinical trial in which he planned to implant human embryos which had been modified using CRISPR‐Cas9. 64 Within days, the world learned that not only had edited embryos been implanted, two baby girls, Lulu and Nana, had already been born. 65

He used CRISPR‐Cas9 to create a nonspecific sequence alteration in the CCR5 gene. CCR5 is a seven‐transmembrane–spanning G protein–coupled CC chemokine (β chemokine) receptor. When expressed on the surface of a human T cell, CCR5 is the main coreceptor (along with CD4) for the human immunodeficiency virus (HIV). A naturally occurring 32–base pair deletion (with heterozygote allele frequencies of about 10% in people with European origin), known as CCR5∆32 , has been shown to disable the protein; 66 heterozygosity of the CCR5∆32 allele has been shown to slow disease progression, while homozygosity significantly increases disease resistance. He's goal was to knock out CCR5 , with the desired outcome of creating HIV‐resistant babies (it should be noted that HIV infection in CCR5∆32 +/+ individuals has been increasingly reported, associated with X4‐trophic HIV strains—that is, strains that rely exclusively on coreceptor CXCR4 for endocytosis, rather than CCR5 67 ).

He presented the details of his investigation 68 at the Second International Summit on Human Genome Editing, being held “to discuss scientific, medical, ethical, and governance issues associated with recent advances in human gene‐editing research.” 69 While his manuscript describing the trial was not accepted by any publications, excerpts are available to the public, and various media outlets (and some experts) have been able to view the paper and supplementary data in their entirety. Enough is now known about He's work that it can serve as the basis of a conversation about the ethics surrounding germline gene editing. There are a number of issues—those inherent in the technologies themselves, as well as scientific hurdles that need to be overcome—before initiating clinical trials, to ensure that they are carried out as ethically as possible.

2.1. Not all sequence variations are created equally

CCR5∆32 has been researched extensively, but is one of only a few CCR5 variants studied. In his abstract, He claims that his team has reproduced this natural variant, but this is not the case: Two embryos were implanted, one of which (Nana) had frameshift mutations on both alleles (a 1–base pair insertion and a 4–base pair deletion, respectively) and the other of which (Lulu) showed a 15–base pair deletion on only one allele. Frameshift mutations have a high probability of disrupting protein structure (and thus function). The 15–base pair deletion, however, will result in five missing amino acids when the protein is translated, and its effect on the protein's function is unknown. He's team could have frozen the embryos, duplicated the sequence alterations in other cell lines, and tested whether or not the genetic changes actually conferred disease resistance, before actually implanting the embryos, but it does not appear that they made an effort to fully understand the actual effect of the alterations they had made. 64 With all of the risks associated with the CRISPR editing process, embryos should not be implanted if the scientists are unsure of the effects.

2.2. Mosaicism

A CRISPR‐Cas vector is inserted into a zygote soon after fertilization. If the CRISPR‐induced mutagenesis only occurred during the single‐cell stage, each successive round of cleavage would yield genetically identical cells. However, while the half‐life of the Cas proteins themselves may not be long, the vectors will remain and continue to be transcribed for days. During this time, the embryo will continue to divide, eventually forming a blastocyst of a few hundred cells. Uneven distribution of the plasmid and the RNPs means that there is a significant potential for mosaicism.

In He's laboratory, three to five cells were removed from each blastocyst, and their genomes sequenced. If Lulu's embryo were made up of identical cells (with one wild type allele and one with a 15–base pair deletion) as He had reported, the Sanger chromatogram should have shown two sets of peaks, approximately the same height. However, it appears likely that there were actually three different combinations of alleles: two normal copies, one normal copy and one with a 15–base pair deletion, and one normal copy and an unknown large insertion. Similarly, while Nana's embryo should have shown two alterations, the Sanger chromatogram revealed three. 70

The suspicion of mosaicism is borne out when sequencing of samples from the cord blood, umbilical cords, and placentas are reviewed. Just as with the embryo sequencing, rampant mosaicism is evident. It is reasonable to assume that the girls’ bodies are mosaic as well, but for an unknown reason, He's team did not test any cells from the girls themselves. 70 There is therefore the possibility that not all of the cells in Nana's body will have modifications to both CCR5 alleles, meaning it is possible that Nana is not actually resistant to HIV.

Mosaicism can have myriad effects: Even a few mutated cells in an organ can cause disease, a single cell can develop into a tumor, and any allelic variation in germ cells will be inherited by the following generation. There is no way to sequence a cell's genome without destroying the cell itself; as such, it is currently impossible to rule out mosaicism in a blastocyst.

2.3. Off‐target effects

As efficient as CRISPR is, there is a high probability of OTMs. He's team reported that in addition to the CCR5 gene edits, there was only one OTM, a 1–base pair insertion in a noncoding region of Chromosome 1 in Lulu's genome. This was based on their relatively limited sequencing, however; as noted above, mosaicism cannot be ruled out. (It should also be noted that there were flaws in the sequencing itself, so there may be other alterations that were missed in the screening, on top of the mosaicism. 70 )

2.4. Other consequences of target gene modification

When undertaking to knock out a gene in an embryo, it is vital to understand all of the functions of that gene.

CCR5 is a chemokine receptor that mediates leukocyte chemotaxis, and thus helps mount immune response. It is therefore unsurprising that homozygosity for the CCR5∆32 variant has been shown to be significantly correlated with more symptomatic infection and higher mortality rates in patients with West Nile virus, 71 influenza A, 71 , 72 and tick‐borne encephalitis. 73 It has also been shown to be associated with upregulation of certain CC chemokine ligands, and in turn associated with progressive reduction in survival time for patients with multiple sclerosis (MS). 74 Is it ethical to create a sequence variation that confers resistance to one illness, while increasing the likelihood of succumbing to another?

Public health conversations will need to change as well. It is possible, for example, that some with a CCR5 edit will engage in riskier sexual practices, or that some with a PCSK9 edit (which is associated with decreased levels of low‐density lipoprotein cholesterol, or LDL, in the blood 75 , 76 ) will be less likely to make behavioral changes such as increased exercise and diet modification.

2.5. Which genes/diseases to target?

Many who have viewed He's work have questioned why he chose to focus on CCR5 and HIV resistance. HIV prevalence in China is relatively low, 77 and current treatments can keep viral loads at almost undetectable levels. He stated that his research could help tamp down the HIV/AIDS epidemic; the most hard‐hit areas (such as Africa), however, would likely not gain much benefit from gene‐editing technologies.

Per a December 2018 poll, 78 Americans draw the line at so‐called enhancement, but favor the use of genetic engineering to address disease and disability. Which diseases and disabilities to target, however, is still an open discussion. Some questions that may help inform that decision: Should there be a focus on infectious disease resistance? Only fatal conditions? Will we decide that there is a need to quantify the degree of suffering? If an effective treatment already exists, should we still seek prevention through genetic modification? Is childhood versus adulthood onset of illness an important factor? Not all sequence variants are guaranteed to cause disease (eg, BRCA genes); should they be considered? What about orphan diseases? And should certain types of disabilities be prioritized over others?

2.6. OTHER ISSUES

2.6.1. clinical research ethics.

The history of research using human subjects has been blemished by unethical treatment of the subjects themselves. From Imperial Japan to the Tuskegee Institute, examples of atrocities committed in the name of medical science can be found across the world. As a result, a number of guidelines have been developed to facilitate ethical research going forward. 79 Nazi Germany engaged in abominable human experimentation during World War II; in 1947, the Nuremberg Military Tribunal (during which Nazi physicians and administrators were tried for war crimes and crimes against humanity) resulted in the Nuremberg Code, a statement aimed at preventing such abuses in the future. Stemming from a reaction to the same offenses, the World Medical Association produced Ethical Principles for Medical Research Involving Human Subjects —known as the Declaration of Helsinki—in 1964 (it has been modified a few times since), which in 1982 was adapted by the Council for International Organizations of Medical Sciences into a manual, Proposed International Ethical Guidelines for Biomedical Research Involving Human Subjects , as a guideline for World Health Organization (WHO) member countries. (Individual countries have created their own guidelines, as well. In the United States, for example, the National Research Act of 1974 established the National Commission for the Protection of Human Subjects of Biomedical and Behavioral Research—often referred to as the Belmont commission—which issued the 1979 Ethical Principles and Guidelines for the Protection of Human Subjects of Research , now known as the Belmont Report. The National Research Act of 1974 also established a set of regulations regarding human subject research; by 1991, after various updates and additions, the government decided that the regulations should become a “Common Rule” covering all federally connected research, codified in Title 45, Part 46 of the Code of Federal Regulations.)

This article will not delve into all of He's ethical missteps as regards his research (such as the fact that he registered the trial with the Chinese Clinical Trial Registry in November 2018, after the twins had already been born). However, there are a few key issues, directly addressed by at least one of these major reports, which can be considered in terms of guiding future ethics discussions regarding gene‐editing clinical trials.

First and foremost, clinical trial participants should be informed of all of the associated risks and benefits. There is significant ambiguity as to the informed consent process in He's study. First, the experiment was misleadingly couched as an HIV vaccine trial. 65 , 80 It is also unclear how much the parents in He's study understood about risks such as mosaicism or increased susceptibility to other infections. The investigator is responsible for keeping participants informed throughout the study; it does not appear that in this case they were informed of the mosaicism present in both embryos (in his presentation at the human genome editing summit, He said only that the parents had been informed about one OTM 68 and does not even mention the mosaicism in his manuscript 70 ). It is likely that were the parents fully informed, they would have decided not to implant one or both embryos. This raises another question: Should parents be the ones to make such a decision, or is that the responsibility of the researchers and doctors?

The selection of the study participants is an issue, as well: The first inclusion criterion is that the participants must be a married couple wherein the husband is HIV‐positive and the wife is HIV‐negative. 81 Father‐to‐child transmission of HIV is rare (especially when the father is on antiretroviral therapy and the mother is on preexposure prophylaxis), but it is possible; for this reason, many couples opt for sperm washing (to separate the sperm from the virus), followed by either in vitro fertilization (IVF) or intrauterine implantation (IUI). While there is no explicit law against HIV‐positive parents accessing these procedures, it is unlikely that it would be approved by hospitals’ ethics committees. 82 Chinese couples often travel to other countries (such as Thailand) for the procedure, but it can cost hundreds of thousands of yuan. 83 The couples selected for He's study may have seen participation as their only chance to have children—indeed, He described the father as having “lost hope for life.” 68 This makes them particularly vulnerable to exploitation. (This may also have informed their decision to implant both embryos rather than just the one that had alterations to both alleles.)

Study participants should be able to voluntarily withdraw from the research at any point; He's informed consent form stipulates that were the couple to withdraw from the study (at any point between the implantation of the embryo in the first IVF cycle and 28 days postbirth), they would be responsible for reimbursing the laboratory for all project costs (and that if reimbursement was not received within 10 calendar days of withdrawal, a substantial fine—more than the average annual income of a Chinese citizen—would be imposed). 80 This is sufficiently cost prohibitive as to prevent a subject from withdrawing from the study.

It is unclear whether He's research actually underwent an ethics review process: In his manuscript, He claims that the Medical Ethics Committee of the Shenzhen Harmonicare Women's and Children's Hospital approved the study in March 2017, but only elaborates by stating that his team was “… told that the committee held a comprehensive discussion of risks and benefits… During the study, the director of the ethics committee was constantly updated about the state of the clinical trial.” 84 The hospital has since denied that the study was reviewed at all, and claims that the signatures on the approval were forged. 85 What is clear is that a number of regulations were violated or circumvented, including the guidelines for embryo research which allow an edited embryo to be cultured for no more than 14 days and prohibit its implantation, 86 as well as the aforementioned limitations on assisted reproductive services for HIV‐positive parents. 82 It is likely that He switched blood samples and kept many of the IVF technicians and obstetricians in the dark as to the nature of the study to get around these issues. 87

Finally, it is reasonable to consider whether He was qualified to be the investigator on such a trial: He had published one paper about CRISPR (in 2010, before human gene editing was an application of the technology), his background was in physics (he crossed over into biophysics), and he had no medical training. This is especially concerning as biohackers have made available both the equipment and the basic blueprints for home CRISPR editing (see the Other Perspectives section)—including advice on how to obtain human embryos and eventually implant them. 88

2.6.2. Socioeconomic disparities

Multiple polls have shown that the majority of people around the world are opposed to the use of genetic engineering of embryos for enhancement, such as athletic ability and intelligence, or for altering physical characteristics, such as eye color and height. 89 It is easy to conceive of the risk of a new age of eugenics.

But even the application of genetic modification to address medical needs holds the potential for establishing inequality. The technology will remain incredibly expensive for some time, prohibitively so for most people. CCR5 edits lie in an ill‐defined area between medical need and enhancement; an unfair health advantage will be established if such modifications are only accessible to the wealthy. Other kinds of edits may mean the difference between life and death; should potentially life‐saving therapies only be available to those with financial means? Put another way, should those individuals on one side of the growing socioeconomic gap be the only ones protected from the suffering that comes with illnesses such as Alzheimer's disease, Huntington disease, or cystic fibrosis?

2.6.3. Possible stigma

Especially while the concept is still novel, it is difficult to predict how society will feel about gene‐edited babies. Will Nana and Lulu face any sort of backlash? Conversely, if and when gene editing becomes commonplace, will there be a stigma associated with not having been edited in some way, such as still being susceptible to various infectious diseases? Might children like Lulu be less accepted for not carrying a desired modification? He wanted to spare HIV‐infected individuals’ children the stigma and discrimination their parents endured; 90 it is possible that having edited genes has replaced one potential stigma with another.

2.6.4. Insurance

Because gene editing will be a tool to cure and prevent illness, insurance coverage will be an important part of the conversation. First, will insurance cover the editing itself? If so, will germline versus somatic cell editing be an important distinction? Will coverage be based on the targeted illness or disability (and expected associated costs)? And who will decide which edits are considered medically necessary and which are considered elective?

Once babies born from edited embryos are born, more questions arise. Will those whose genes have not been edited to prevent certain illnesses be considered to have preexisting conditions? Will they be expected to pay more for coverage? On the other side of the coin, will those who have had their genes edited (especially when the technology is first rolled out) pay more because of possible off‐target risks or potential negative consequences of editing (eg, the increased susceptibility to influenza associated with CCR5 editing)?

2.6.5. Other perspectives

A full discussion of ethics requires a balanced presentation of various points of view.

There are those who object to continued research into gene editing, especially in zygotes, for myriad reasons. For example, some feel that gene editing is “playing God” and that it is not man's role to make changes to the basic building blocks of humanity; others are concerned about the potential that the technology, once perfected, could be co‐opted to produce designer babies; there is the consideration that opening a market for human eggs for research could lead to exploitation of disadvantaged women; and still others have concerns similar to those who are opposed to embryonic stem cell research—such as the conviction that embryos should not be created for the purpose of research, or that un‐implanted embryos (which they consider potential life) should not be destroyed.

There are also those who believe that not only should research continue, but that even nascent technology such as gene editing should be accessible to the public. 91 Known as biohackers, these scientists and activists laud the efforts like Jiankui He's. 88 Educational and laboratory materials are currently available to essentially anyone. It is even possible to purchase CRISPR kits, 92 and while a new California law requires that such kits are labeled “not for self‐administration” 93 there are currently no laws prohibiting people from doing just that—in fact, the owner of one company was investigated by the California Medical Board for unlicensed practice of medicine after injecting himself with CRISPR, but the investigation was dropped after four months with “no further action… anticipated.” 94

3. GLOBAL DISCUSSIONS ON GERMLINE EDITING

While it is impossible to mandate that all countries follow the same set of guidelines, it is possible to establish guiding principles for the risk‐benefit analyses and ethical discussions each country will undertake in developing their own regulatory framework. Because science moves faster than regulation, the scientific community as a whole can also use these principles to help guide ethically charged research decisions where no regulations yet exist. To that end, various groups have been meeting all over the world to try to come to a consensus on how to proceed with germline editing research and the potential clinical applications thereof.

3.1. Before He’s announcement

In 2015, the International Bioethics Committee (IBC), part of the United Nations Educational, Scientific, and Cultural Organization (UNESCO), released the Report of the IBC on Updating its Reflection on the Human Genome and Human Rights. 95 The report considers other technologies as well, but “recommends a moratorium on genome editing of the human germline.”

Also in 2015, investigators in China announced that they had successfully used CRISPR to edit a nonviable human embryo. 96 This inspired the first International Summit on Human Gene Editing, held December 2015 in Washington, D.C. Hosted by the US National Academy of Sciences, US National Academy of Medicine, the Royal Society of the UK, and the Chinese Academy of Sciences, the summit brought together more than 3500 stakeholders (500 in person and 3000 online) from around the world to discuss human gene editing. At the end of the summit, the organizing committee released a statement advising ongoing global engagement and discussion, and outlined their conclusions regarding gene editing: 97 “(i)ntensive basic and preclinical research is clearly needed and should proceed, subject to appropriate legal and ethical rules and oversight…”; “(m)any promising and valuable clinical applications of gene editing are directed at altering genetic sequences only in somatic cells… [and] they can be… evaluated within existing and evolving regulatory frameworks for gene therapy…”; and “(g)ene editing might also be used, in principle, to make genetic alterations in gametes or embryos…” The statement goes on to address the ethical, legal, and scientific questions surrounding germline editing that have yet to be answered, and warns:

It would be irresponsible to proceed with any clinical use of germline editing unless and until (a) the relevant safety and efficacy issues have been resolved, based on appropriate understanding and balancing of risks, potential benefits, and alternatives, and (b) there is broad societal consensus about the appropriateness of the proposed application. Moreover, any clinical use should proceed only under appropriate regulatory oversight. At present, these criteria have not been met for any proposed clinical use: the safety issues have not yet been adequately explored; the cases of most compelling benefit are limited; and many nations have legislative or regulatory bans on germline modification. However, as scientific knowledge advances and societal views evolve, the clinical use of germline editing should be revisited on a regular basis.

While this statement in no way gives a green light for trials such as He's, it also does not call for an outright moratorium. In March 2017, another Chinese team published the results of the first use of CRISPR in viable human embryos. 98 Less than two years later, He's work was revealed to the world.

3.2. After He’s announcement

The article about He's trial was published the day before the second International Summit on Human Gene Editing. As they had at the first summit, organizers released a concluding statement on the last day. Surprisingly, not only does the statement again fall short of calling for a moratorium on clinical use of gene editing, the language is even softer than that of the first summit statement:

The variability of effects produced by genetic changes makes it difficult to conduct a thorough evaluation of benefits and risks. Nevertheless, germline genome editing could become acceptable in the future if these risks are addressed and if a number of additional criteria are met. These criteria include strict independent oversight, a compelling medical need, an absence of reasonable alternatives, a plan for long‐term follow‐up, and attention to societal effects. Even so, public acceptability will likely vary among jurisdictions, leading to differing policy responses. The organizing committee concludes that the scientific understanding and technical requirements for clinical practice remain too uncertain and the risks too great to permit clinical trials of germline editing at this time. Progress over the last three years and the discussions at the current summit, however, suggest that it is time to define a rigorous, responsible translational pathway toward such trials.

In December 2018, seeing the need for a more substantial framework of regulatory guidance, the WHO established the Advisory Committee on Developing Global Standards for Governance and Oversight of Human Genome Editing, “a global, multi‐disciplinary expert panel to examine the scientific, ethical, social and legal challenges associated with human genome editing… tasked to advise and make recommendations on appropriate institutional, national, regional and global governance mechanisms for human genome editing.” 99 They have established the Human Genome Editing Registry to collect information on human clinical trials involving genome editing, and the WHO has supported the advisory committee's interim recommendation that “it would be irresponsible at this time for anyone to proceed with clinical applications of human germline genome editing.” 100

In 2019, the US National Academies of Medicine and Science, together with the Royal Society, convened the International Commission on the Clinical Use of Human Germline Genome Editing. The goal of commission is: 101

… with the participation of science and medical academies around the world, to develop a framework for scientists, clinicians, and regulatory authorities to consider when assessing potential clinical applications of human germline genome editing. The framework will identify a number of scientific, medical, and ethical requirements that should be considered, and could inform the development of a potential pathway from research to clinical use—if society concludes that heritable human genome editing applications are acceptable.

The commission's final report is scheduled to be released in the spring of 2020.

As the science progresses, there are clearly significant conversations yet to be had.

CONFLICT OF INTEREST

The authors have stated explicitly that there are no conflicts of interest in connection with this article.

Rothschild J. Ethical considerations of gene editing and genetic selection . J Gen Fam Med . 2020; 21 :37–47. 10.1002/jgf2.321 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]

Top 10 Genetic Testing Methods for Rare Diseases

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3. Targeted Gene Panels

Targeted gene panels focus on genes associated with rare diseases. These panels are tailored to diagnose known genetic conditions more efficiently and affordably than broader sequencing approaches.

4. Chromosomal Microarray Analysis (CMA)

Chromosomal microarray analysis identifies large chromosomal abnormalities such as deletions or duplications, which may not be detectable with traditional karyotyping. It is especially valuable for diagnosing developmental delays and congenital anomalies.

5. Sanger Sequencing

Sanger sequencing is used to confirm specific mutations discovered through other genetic testing methods. It is a precise technique commonly used for validating genetic variants identified in broader testing.

6. Biochemical Testing

Biochemical testing examines proteins or metabolites to detect enzymatic deficiencies or abnormalities, crucial for diagnosing metabolic disorders where specific metabolites indicate a genetic condition.

7. Mitochondrial DNA Testing

Mitochondrial DNA testing focuses on the DNA in mitochondria, inherited maternally, to diagnose mitochondrial disorders. These disorders can affect multiple body systems and present diverse symptoms.

8. RNA Sequencing (RNA-seq)

RNA sequencing analyzes gene expression and identifies mutations affecting RNA splicing. It provides functional insights into diseases, especially those involving abnormal gene expression.

9. Prenatal Genetic Testing

Prenatal genetic testing, including non-invasive prenatal testing (NIPT) and chorionic villus sampling (CVS), screens for genetic conditions in the fetus. It enables early identification of chromosomal abnormalities, aiding informed decision-making.

10. Newborn Screening

Newborn screening involves testing infants shortly after birth for a panel of genetic and metabolic disorders. This early detection allows for prompt intervention and treatment, significantly improving outcomes for conditions that can be managed effectively if caught early, such as spinal muscular atrophy (SMA).

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In conclusion, the diverse types of genetic testing for rare diseases—including Whole Genome Sequencing, Whole Exome Sequencing, and targeted gene panels—offer comprehensive tools for accurate diagnosis and timely intervention. These methods collectively enhance early detection and personalized treatment, significantly improving outcomes for patients with rare genetic conditions.

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Genetic Testing, Essay Example
Genetic testing may have limited useful and reliable applications especially in the case of diseases whose genes are few and have been correctly identified. Huntington gene is one example. People with Huntington disease have 36 to more than 120 CAG (Huntington disease is also known as CAG trinucleotide repeat expansion). People with 36 to 40 ...
Conclusion
11. Conclusion. As discussed throughout this report, human health is determined by the interaction of several factors, including the social environment, genetic inheritance, and personal behaviors. Socioeconomic status, race/ethnicity, social networks/social support, and the psychosocial work environment all have been shown to affect health ...
Social, Legal, and Ethical Implications of Genetic Testing
Each new genetic test that is developed raises serious issues for medicine, public health, and social policy regarding the circumstances under which the test should be used, how the test is implemented, and what uses are made of its results. ... Some newborn screening programs store filter papers in a temperature-controlled, secure setting ...
Genetic Testing: The Key Aspects
Genetic Testing: The Key Aspects Essay. Examining DNA, the chemical database that contains instructions for a patient's body's functioning is a component of genetic testing. Genes may have changed (mutated), which could result in sickness or illness, according to genetic testing (Macha & McDonough, 2011).
Impact of Genetic Testing on Human Health:
Applied Clinical Genomics is the application of genetic information to the clinical setting, including improved diagnosis of disease and tailored treatment efficacy and safety. By discovering and defining the genes that underlie susceptibility to disorders, genetic information can be used to identify and better define those genes that play ...
Advantages and Disadvantages of Genetic Testing: Essay Example
Advantages and Disadvantages of Genetic Testing: Essay Conclusion. In general, the advantages and disadvantages of genetic testing are numerous, and people have to understand that it is impossible to predict the results, as well as to be ready for the information. Serious decisions should be made, and significant steps should be taken by people ...
The Ethical Implications of Genetic Testing
Conclusion. Genetic testing is growing really fast in this field of genetics. Because it becomes bigger many legal, ethical and social issues arise.Testing can be used to diagnose possible future deseases, find unknown diseases or to test if you should make a baby with your partner.
Ethics of Genetic Testing
It includes the fee for IVF-averaging $8,000 per cycle-plus the cost of genetic testing, which adds an estimated $2,000. Even in the rare cases when IVF expenses are paid by health insurance, the genetic component is not covered. Costs are also likely to be high in the even more advanced procedures now being proposed.
Genetic Testing: Advantages and Disadvantages Essay
Get a custom essay on Genetic Testing: Advantages and Disadvantages. At the same time, I acknowledge all the benefits that genetic testing can bring in terms of diagnosing a wide range of diseases and conditions. Fearing that they might discover hereditary predispositions to some untreatable diseases, many people choose not to get tested.
Ethics of Genetic Testing
As noted by Miller, (2007), genetic screening entails the systematic establishment of hereditary health risks that a person may have and thus may be used to discriminate people with high risk traits from the employment. Although it is true that the concept of genetic testing has many ethical concerns, the greatest concern of genetic testing at ...
The genetic basis of disease
Genetics plays a role, to a greater or lesser extent, in all diseases. Variations in our DNA and differences in how that DNA functions (alone or in combinations), alongside the environment (which encompasses lifestyle), contribute to disease processes. ... Essays Biochem. 2018 Dec 2;62(5):643-723. doi: 10.1042/EBC20170053. Print 2018 Dec 3 ...
The genetic basis of disease
Genetics plays a role, to a greater or lesser extent, in all diseases. Variations in our DNA and differences in how that DNA functions (alone or in combinations), alongside the environment (which encompasses lifestyle), contribute to disease processes. This review explores the genetic basis of human disease, including single gene disorders, chromosomal imbalances, epigenetics, cancer and ...
Ethical Issues in Genetic Testing
Conclusions. Genetic testing is poised to play a greater and greater role in the practice of obstetrics and gynecology. To assure patients of the highest quality of care, physicians should be familiar with the currently available array of genetic tests, as well as with their limitations. They also should be aware of the untoward consequences ...
Genetic Testing: Ethical Aspects
Genetic medicine is indeed a multidisciplinary matter that covers broad contexts, sometimes transversely. Its extreme complexity, coupled with possible perceived repercussions on an individual's life, involves important issues in the ethical, deontological and legal medical field. The aspects related to the execution of genetic testing have ...
Genetic Testing Essays (Examples)
The genetic testing is used to measure the percentage or level of any risk associated to one's life. By studying gene mutation, it is predictable that a certain disease is likely to be occurring in future. However you may not find any symptoms of diseases until you do not suffer from it. (Mayo clinic staff, 2006).
Essay on Genetics (For College and Medical Students)
1. Essay on the Meaning of Genes: The term 'gene' was coined by Danish botanist Wilhelm Johannsen in 1909. It is the basic physical and functional unit of heredity. Heredity is the transfer of characters from parents to their offspring that is why children resemble their parents.
Genetic Testing Essay
Genetic Testing Essay. Decent Essays. 809 Words. 4 Pages. Open Document. In recent discussions of genetic testing, a controversial issue has been whether genetic testing is effective in helping find cure of some diseases. On the one hand, some argue that genetic testing helps us detect genetically passed diseases from parents to children. .
Genetic Testing Essay
Genetic Testing Essay; Genetic Testing Essay. Sort By: Page 1 of 50 - About 500 essays. Decent Essays. The Benefits Of Genetic Testing. 1175 Words; 5 Pages ... Genetic testing, also known as screening, is a rapidly advancing new scientific field that can potentially revolutionize not only the world of medicine, but many aspects of our lives. ...
Nursing Ethics of Genetic Testing and Research Essay
Genetic discrimination is another critical challenge in genetic testing and study. A nurse must accept their duty for ensuring that patients understand the hazards of genetic discrimination and are aware of their legal rights to protect themselves from discrimination. Nurses must also campaign for regulations that prevent genetic discrimination.
213 Genetics Research Topics & Essay Questions for College ...
213 Genetics Research Topics & Essay Questions for College and High School. Genetics studies how genes and traits pass from generation to generation. It has practical applications in many areas, such as genetic engineering, gene therapy, gene editing, and genetic testing. If you're looking for exciting genetics topics for presentation, you ...
Genetics Essays: Examples, Topics, & Outlines
Find inspiration for topics, titles, outlines, & craft impactful genetics papers. Read our genetics papers today! Homework Help; Essay Examples ... The Rita and Peter Trosack and Tay-Sachs Disease Genetic testing is becoming a much more common practice in medicine today. This presents a unique set of challenges for medical professionals in ...
Genetic Testing Essay Examples
Genetic Testing Essays. Comprehensive Strategies for Active Labor Management. As the nurse attending to Mrs. Wong and her husband, collecting priority data is crucial to tailor interventions that meet their unique needs. I would inquire about Mrs. Wong's current physical condition and any symptoms she may be experiencing related to her early ...
Ethical considerations of gene editing and genetic selection
Preimplantation genetic testing was ideated eleven years before the birth of the first in vitro fertilization (IVF) baby in 1978. ... and outlined their conclusions regarding gene editing: 97 "(i)ntensive basic and preclinical research is clearly needed and should proceed, subject to appropriate legal and ethical rules and oversight ...
Top 10 Genetic Testing Methods for Rare Diseases
It is a precise technique commonly used for validating genetic variants identified in broader testing. 6. Biochemical Testing. Biochemical testing examines proteins or metabolites to detect enzymatic deficiencies or abnormalities, crucial for diagnosing metabolic disorders where specific metabolites indicate a genetic condition. 7.
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A Texas judge once again blocked the release of A-F accountability grades for public schools that were to be published Thursday. The order comes in response to a lawsuit from a handful of ...