Bioethics for clinicians: 14. Ethics and genetics in medicine

Information about a patient''s inherited risk of disease has important ethical and legal implications in clinical practice. Because genetic information is by nature highly personal yet familial, issues of confidentiality arise. Counselling and informed consent before testing are important in view of the social and psychological risks that accompany testing, the complexity of information surrounding testing, and the fact that effective interventions are often not available. Follow-up counselling is also important to help patients integrate test results into their lives and the lives of their relatives. Genetic counselling should be provided by practitioners who have up-to-date knowledge of the genetics of and the tests available for specific diseases, are aware of the social and psychological risks associated with testing, and are able to provide appropriate clinical follow-up. Some physicians may elect to refer patients for genetic counselling and testing. However, it is inevitable that all physicians will be involved in long-term follow-up both by monitoring for disease and by supporting the integration of genetic information into patients'' lives.     

Training for genetic counsellors

Genetic counsellors are uniquely trained to provide support, explanations and guidance to individuals or families who have been diagnosed with a genetic disorder. As our knowledge of the genetic basis of disease increases, so does our ability to diagnose it and so does the demand for appropriately trained genetic counsellors. Despite this growing demand, only a handful of countries provides formal courses in genetic counselling, whereas other countries leave genetic counselling in the hands of medical practitioners or medical geneticists.     

Women's need for information before attending genetic counselling for familial breast or ovarian cancer: a questionnaire,interview, and observational study.

OBJECTIVES: To describe women''s information needs prior to genetic counselling for familial breast or ovarian cancer. DESIGN: Prospective study including semistructured telephone interviews before genetic counselling, observations of consultations, completion of postal questionnaires, and face-to face interviews within two months of counselling. SUBJECTS: 46 women attending genetic counselling for familial breast or ovarian cancer. MAIN OUTCOME MEASURES: Subjects'' understanding of process and content of genetic counselling before attending and attitudes about their preparation for the counselling session. RESULTS: Although all women interviewed before the clinic expected to discuss their risk of developing cancer and risk management options, there was evidence of a lack of knowledge about the process and content of genetic counselling, 17 (37%) women said they did not know what else would happen. Most women interviewed after counselling viewed it positively, but 26 (65%) felt they had been inadequately prepared and 11 (28%) felt that their lack of preparation meant that they could not be given an accurate estimation of their risk of cancer. CONCLUSIONS: Some women felt that they did not obtain optimum benefit from genetic counselling because they were inadequately prepared for it. We suggest that cancer family history clinics should provide women with written information about the process and content of genetic counselling before their clinic attendance.     

Psychological implications of family studies by molecular biology. An example--muscular dystrophy

A dialogue between a geneticist and a M.D. trained in medical psychology has been established about problems arising in genetic counselling. A better knowledge of themselves allows them to increase the quality of genetic counselling by improving the communication techniques. The whole personality and not only the genetic disease of the individuals seeking genetic counselling is taken into account during the counselling process.     

Genetic diversity and disease susceptibility.

The range of genetic diversity within human populations is enormous. Genetic susceptibility to common chronic disease is a significant part of this genetic diversity, which also includes a variety of rare clear-cut inherited diseases. Modern DNA-based genomic analysis can now routinely lead to the identification of genes involved in disease susceptibility, provides the basis for genetic counselling in affected families, and more widely for a genetically targeted approach to disease prevention. This naturally raises problems concerning the use of information on an individual''s decisions, but for employment, and health and life insurance.     

Génétique et infertilité masculine: données actuelles

Intracytoplasmic sperm injection (ICSI) and testicular biopsies (TESE) have revolutionized the treatment of male infertility, introducing a risk of an increased frequency of genetic defects in the offspring. These risks and their consequences must therefore be evaluated when proposing ICSI to an infertile man. Karyotype and molecular analysis should be performed to detect any genetic defects responsible for male infertility. Y microdeletion screening is important, not only to define the aetiology of spermatogenic failure, but also to provide information allowing a more appropriate management of both the infertile male and his future male child. Genetic counselling is then advised before deciding to attempt ICSI.     

Privacy and Property Issues for a Familial Cancer Service

Approximately 1 in 30 people develop cancer due to an underlying familial predisposition. Genetic counselling and testing for people with (and at risk of) familial cancer are becoming more widely available, but service providers need to address challenging issues in relation to privacy and property. As in any counselling situation, a genetic counsellor seeks to ensure that the principles of autonomy, confidentiality, beneficence, and equity operate in favour of the client. But in dealing with a familial disorder, the application of these principles to the individual must be balanced with the potential for these principles to apply to other family members. This paper summarises the recent experience of a familial cancer service in seeking to avoid situations in which these principles, operating for both individual clients and their relatives, can come into conflict.     

Prospective study of genetic counselling.

A prospective study was carried out on 200 consecutive subjects seen for counselling (consultands) for serious genetic disorders. Educational and social background of consultands and their knowledge and understanding of their particular problem were assessed before counselling, and their response was determined immediately afterwards and three months and two years later by an independent observer not concerned in the genetic counselling. The husband''s educational background was particularly important in influencing a couple''s comprehension of counselling. X-linked recessive and chromosomal disorders presented the most difficulties in comprehension. The counsellors'' assessment of comprehension was a good guide to the consultands'' comprehension as assessed at subsequent follow-up. The proportion deterred from having children increased with time and over a third had been sterilised within two years of counselling. It is suggested that follow-up after counselling should be routine, especially when the counsellor suspects that comprehension has not been good, in X-linked recessive and chromosomal disorders, and when the risks of having an affected child are considered to be high.     

基于SRAP标记的墨西哥落羽杉优良单株的遗传多样性分析

采用SRAP标记方法,分析了原产地及种植地不同的18个墨西哥落羽杉(Taxodium mucronatum Tenore)优良单株的遗传多样性,并根据遗传相似系数、采用UPGMA法对它们的遗传关系进行了聚类分析.结果显示:用7对引物组合从18个单株的总DNA中共扩增出87条带,其中多态性条带71条,多态性条带百分率为81.6％.按照原产地和种植地可将18个单株分为4组,它们的总体Nei's基因多样性指数、Shannon信息指数和基因分化系数分别为0.229、0.355和0.479 9,而基因流仅为0.542,说明各组间的基因交流较少.18个单株间的遗传相似系数为0.632 2～0.919 5,平均值为0.753 9.聚类分析结果显示:18个单株可分为3组,其中18号和14号单株分别单独成组,其余16个单株聚为1组.后者可进一步分为8个亚组:1号、7号、12号和15号单株各自单独成亚组;2号、3号、5号、9号、11号和13号单株聚为1个亚组;4号和6号单株、8号和17号单株、10号和16号单株分别聚为3个亚组.研究结果表明:18个优良单株间存在丰富的遗传变异,但它们的遗传关系与原产地及种植地明显不相关.     

Role of propagule pressure in colonization success: disentangling the relative importance of demographic,genetic and habitat effects

High propagule pressure is arguably the only consistent predictor of colonization success. More individuals enhance colonization success because they aid in overcoming demographic consequences of small population size (e.g. stochasticity and Allee effects). The number of founders can also have direct genetic effects: with fewer individuals, more inbreeding and thus inbreeding depression will occur, whereas more individuals typically harbour greater genetic variation. Thus, the demographic and genetic components of propagule pressure are interrelated, making it difficult to understand which mechanisms are most important in determining colonization success. We experimentally disentangled the demographic and genetic components of propagule pressure by manipulating the number of founders (fewer or more), and genetic background (inbred or outbred) of individuals released in a series of three complementary experiments. We used Bemisia whiteflies and released them onto either their natal host (benign) or a novel host (challenging). Our experiments revealed that having more founding individuals and those individuals being outbred both increased the number of adults produced, but that only genetic background consistently shaped net reproductive rate of experimental populations. Environment was also important and interacted with propagule size to determine the number of adults produced. Quality of the environment interacted also with genetic background to determine establishment success, with a more pronounced effect of inbreeding depression in harsh environments. This interaction did not hold for the net reproductive rate. These data show that the positive effect of propagule pressure on founding success can be driven as much by underlying genetic processes as by demographics. Genetic effects can be immediate and have sizable effects on fitness.     

Determination of genetic relationships among shape Phaseolus vulgaris populations in a conical cross from RAPD marker analyses

Random-amplified polymorphic DNA (RAPD) markers were used to determine genetic relationships among Phaseolus vulgaris breeding populations. Genetic distances were calculated from the distribution of 317 RAPD markers among 8 parents, 10 individuals from 8 cycle-one populations, 10 individuals from 6 cycle-two populations and 10 individuals from 2 cycle-three populations of a conical cross. Genetic distances between populations and parents were consistent with their degree of relationship in the crossing scheme indicating that a RAPD analysis is a sensitive and useful method for categorizing breeding materials according to their genetic similarities. Genetic variation among individuals within populations increased from cycle one to cycle three and variation among populations within the cycles decreased from cycle one to cycle three in the conical cross. The results showed that this crossing scheme can be used to collect the genetic diversity in eight parents into a single plant breeding population. Abbreviations: CBB, common bacterial blight; GD, genetic distance; RAPD, random-amplified polymorphic DNA     

Beyond consent: ethical and social issues in genetic testing

Informed consent is a vital ethical doctrine in clinical medicine and, through genetic counselling, is being applied to genetic testing. But genetic testing raises issues that transcend the traditional concept of informed consent. Genetic tests are adopted without demonstrable clinical benefit, and the consequences of testing can reach beyond the individual to their families and communities. Understanding the social and cultural context of genetic testing will lead to more informed discussion and debate on these issues.     

Genetic tests: between risks and opportunities. The case of neurodegenerative diseases

Commercial genetic testing challenges traditional medical practice and the doctor–patient relationship. Neurodegenerative diseases may serve as the practical and ethical testing ground for the application of genomics to medicine.In the age of the Internet, a wealth of information lies at your fingertips—even your genetic ancestry and your fate in terms of health and sickness. A Google search for ‘genetic testing'' immediately comes up with a list of companies offering quick, direct-to-consumer genetic tests (DCGT) for relatively little money. “Claim your kit, spit into the tube and send it to the lab,” states the website of 23andMe—the company whose Personal Genome Service was named the ‘2008 Invention of the Year'' by Time magazine. Six to eight weeks after sending in a sample, customers can log on to the company website and learn about their genetic origins and ancestry if they opted for the ‘Fill in Your Family Tree'' option, or can explore their genetic profile under the “Health Edition” and what it says about personal disease risks and drug responses.The availability of next-generation high-throughput DNA sequencers has enabled companies to sequence the genes of a large number of customers at a low costs and with few personnel23andMe is one of several companies that offer predictive genetic tests covering a range of multifactorial and monogenic disorders (STOA, 2008). This is clearly a revolutionary approach to personalized medicine; it not only allows individuals to learn about genetic risk factors for a variety of diseases, but also does so outside the established medical system. Before the advent of DCGTs, genetic tests were only carried out at specialized medical institutions under controlled conditions, and only on referral from a physician. The decreasing price of DNA sequencing, new technologies for high-throughput sequencing and the growth of the Internet have all helped to reduce the technical, financial and access barriers to genetic testing. It is therefore not surprising that private enterprises moved into this fast-developing market.The availability of next-generation high-throughput DNA sequencers enables companies to sequence the genes of a large number of customers at a low cost and with few personnel. They can therefore offer this service at attractive prices, in the range of a few hundred dollars. The Internet conversely enables accessibility: a few mouse clicks are enough, while completely bypassing the usual checks and balances of organized healthcare. This means that expert advice is often lacking for patients about results that predict inherited risks for diabetes, cancer, neurological disorders and drug response (STOA, 2008).The simple, affordable and rapid service offered by these companies raises concerns about the clinical validity and utility of the tests, as well as the information and support that they offer to properly interpret the results. In June this year, the US Food and Drug Administration (FDA) contacted five companies that sell genetic tests directly to consumers and asked them to prove the validity of their products (Pollack, 2010). The FDA argues that genetic tests are diagnostic tools that must obtain regulatory approval before they can be marketed, but it did not order the companies to stop selling their tests. 23andMe—one of the five companies that were contacted—replied: “We are sensitive to the FDA''s concerns, but we believe that people have the right to know as much about their genes and their bodies as they choose” (Pollack, 2010). Last year, researchers from the J. Craig Venter Institute (San Diego, CA, USA) and the Scripps Translational Science Institute (La Jolla, CA, USA) reported inconsistencies between results obtained from two DCGT companies in an opinion article in Nature and made recommendations for improving predictions (Ng et al, 2009).A balance must be struck between consumer choice, consumer benefit and consumer protection. On one side is the individual''s right to have access to information about his or her health condition and health risks, so as to be able to take preventive measures. On the other side, serious questions have emerged about the lack of proper counselling in a professional setting. Are customers able to correctly understand, interpret and manage the information gained from a genetic test? Are they prepared to deal with the health risk information such a test provides? Are the scientific community and society as a whole ready to change the focus in medicine from morphological and physiological factors to molecular and genetic information?A balance must be struck between consumer choice, benefit and protectionThese concerns become more complicated when companies offer genetic tests for neurodegenerative disorders for which there are no preventive measures or treatments, such as Alzheimer, Parkinson or Huntington diseases. Most of these diseases are severe, debilitating and can lead to stigmatization and possible discrimination for patients. Brain disorders that cause progressive mental decline affect not only the health of the individual, but also their identity, self-consciousness and role within the family and society. As Judit Sándor, Director of the Centre for Ethics and Law in Biomedicine at the Central European University (Budapest, Hungary) put it: “The stigmatization of hereditary diseases in society may lead to ethical and legal consequences that are difficult to grasp. The stigma associated with neurodegenerative diseases would be even harder to bear if the disease is proven to be hereditary by some form of genetic testing.”In this context, 60 experts from a range of disciplines—scientists, clinicians, philosophers, sociologists, jurists, journalists and patients—from Europe, Canada and the USA met at the 2010 workshop ‘Brains In Dialogue On Genetic Testing'' in Trieste, Italy. The meeting was organized by the International School for Advanced Studies, as part of the European project ‘Brains in Dialogue'', which aims to foster dialogue among key stakeholders in neuroscience (www.neuromedia.eu). The use of predictive genetic testing for neurodegenerative diseases was the main focus of the meeting and represents an interesting model for discussing the risks and benefits of DCGTs.Very few neurodegenerative disorders have a typical Mendelian inheritance. The most (in)famous is Huntington disease, which typically becomes noticeable in middle age. Symptoms include progressive choreiform movements, cognitive impairment, mood disorders and behavioural changes. Huntington disease is caused by an increase in the number of CAG repeats in the gene Huntingtin, which can be tested for easily and reliably (Myers, 2004) in order to confirm a diagnosis or predict the disease, in at-risk groups or prenatally. The results have psychological and ethical implications that affect individuals and their families. According to the STOA report on DCGTs, only one company offers a test for Huntington disease.Most neurodegenerative disorders have a more complex set of genetic and environmental risk factors that make it difficult—if not impossible—to predict the risk of disease at a certain age. A small percentage of cases of Alzheimer and Parkinson diseases—usually early-onset—carry specific mutations with a Mendelian inheritance, but genetic factors are also involved in the most common late-onset forms of these diseases (Avramopoulos, 2009; Klein & Schlossmacher, 2006). Nicholas Wood of University College London, UK, commented that: “[t]here has been a revolution in our molecular genetic understanding of Parkinson''s disease. Twenty years ago Parkinson''s disease perhaps was considered the archetype of non-genetic disease. It is now clear that a growing list of genes is primarily responsible for Mendelian forms of Parkinson''s disease. It is also clear from recent studies that, due to reduced penetrance, some of these ‘Mendelian genes'' play a role in the so-called sporadic disease.” Nevertheless, a genetic test based on susceptibility genes would not enable a clear diagnosis—as in the case of Huntington disease—but only an estimate of the individual''s risk of developing the disease later in life, with varying reliability.For Alzheimer disease, genetic testing is usually only recommended for individuals with a family history of early-onset or with immediate relatives who already have the disease. The most common form of late-onset Alzheimer disease has a complex inheritance pattern. The medical establishment does not therefore recommend genetic testing for it, although a polymorphism in the Apolipoprotein E (APOE) gene has been unequivocally associated with Alzheimer disease (Avramopoulos, 2009). The identification of such risk factors through epidemiological studies provides valuable information about the molecular basis of the disease, but the management of this information at the individual level seems difficult for clinicians and patients. Agnes Allansdottir of the University of Siena, Italy, explained these difficulties stating that “research on decision-making processes demonstrates that we humans have severe problems dealing with probabilities.”Sándor expressed concerns that these difficulties could lead to additional discrimination. “Most people know what to do if they have high blood pressure, for instance. However, information coming from a genetic test is much more complex—their reading and interpretation require special expertise,” she said. She pointed out that some groups might be unable to access that expertise, while others might be unable to understand the information. “As a consequence, they will suffer an additional form of discrimination that is the ‘discrimination in the accessibility'' of sensitive and complex medical data, and that affects […] the right to privacy, as well.”…“research on decision-making processes demonstrates that we humans have severe problems dealing with probabilities”It is certainly possible that individuals who do not understand what probabilistic estimates of risk mean will be upset to find out they have a higher risk of developing a certain disorder, even though in absolute terms this risk is marginal. Avoiding this situation is what genetic counselling tries to achieve: to inform patients and help them to interpret the results of genetic tests. For the same reason, genetic testing for most common forms of late-onset Alzheimer or Parkinson disease—both of which are multifactorial—is not recommended, precisely because of the limited predictive value of these tests and the lack of proven preventive measures. However, various companies including deCODEme offer to identify your APOE variant and calculate “your risk of developing late-onset Alzheimer''s Disease” as part of their service.Research has demonstrated that genetic testing may be a useful coping strategy for some at-risk individuals (Gooding et al, 2006), a conclusion that was also reached by the Risk Evaluation and Education for Alzheimer''s Disease (REVEAL) study (Green et al, 2009). Some results showed that knowledge of their APOE genotype and numerical lifetime risk influenced the health-related behaviour of asymptomatic adult children of Alzheimer disease patients. The discovery of increased risk of disease through an education-and-disclosure protocol was associated with a stronger motivation to engage in behaviours that reduce risk, such as changes in medications or vitamin intake, even if their effectiveness is still unclear (Chao et al, 2008). Genotype disclosure did not result in short-term psychological problems, despite the frightening nature of the disease and the lack of therapies for it (Green et al, 2009). These studies highlight the importance of education and counselling in understanding risk and evaluating the means of counteracting it.Yet the ease with which DCGT companies offer tests over the Internet creates a new kind of autonomy for patients. “Genetic information serves often as a key to future decisions. Based on the information, they may rearrange the priorities in their life or change their lifestyle in order to fight against the manifestation of the disease, to decrease its symptoms or simply delay its progress,” Sándor said. “For many people, nothing else is worse than the lack of certainty and thus knowledge, in itself, can be a value.”To know or not to know: that is the question—particularly for neurodegenerative diseases. In addition to the opinions of the experts at the meeting, the public round table, ‘Health and DNA: my life, my genes'', showed that the choice whether to take a test should be a personal decision; certainly nobody should be forced in one direction or another. During the discussion, different opinions and experiences regarding the use of genetic testing were presented by members of the panel and the public. Verena Schmocker, a Swiss woman affected by Parkinson disease, explained why she refused to be tested, despite a strong family history of early-onset Parkinson disease. “I knew already that the disease was in my family, but I didn''t want to take any genetic test. I chose to live my life day by day and live what is there for me to live.” Another woman in the audience explained that she wanted to know her destiny: “[w]hen 15 years ago I was diagnosed with Huntington''s disease I woke up from a nightmare of doubts. I started organizing my life, I got married and got prepared for the future.”In many ways, Huntington disease is an unrepresentative example—not only because it is an untreatable, debilitating Mendelian disease, but also because patients typically receive mandatory and sophisticated patient counselling. Most importantly, as Marina Frontali from the National Research Council (Rome, Italy) highlighted, counselling should enable and respect autonomous decisions by the person at risk, even in light of third-party pressure to take the test, not just by employers or insurance companies, but also by family members. The counselling service for Huntington disease—through a tight collaboration between laypeople and professionals—is a valuable example of the management of genetic testing.…the ease with which DCGT companies offer tests over the Internet creates a new kind of autonomy for patientsThe Eurobarometer 2005 survey showed that EU citizens are generally supportive of the use of genetic data for diagnosis and research, and 64% of the respondents said that they would take a genetic test to detect potential diseases (EC, 2006). In reality, however, attitudes vary between countries: in most cases, people would be willing to take a test only in exceptional circumstances or only if it was highly regulated and controlled. Interestingly, those countries in which people expressed more concern and negative attitudes towards testing were those with higher levels of education and scientific literacy, where the mass media is more attentive to science and technology and where the public and political debate is more advanced. It shows, again, that increasing scientific literacy is not enough to overcome people''s fears and objections to genetic testing; the more they understand the issues, the less likely people are to be enthusiastic about new technologies.These concerns notwithstanding, the number of tests that are available is growing, and genetic testing—whether as part of the healthcare system or through DCGT companies—is becoming a model for preventive medicine and discussions about the impact of genetics on public health (Brand et al, 2008). The advances brought about by genomics will lead to more targeted health promotion messages and disease prevention programmes specifically directed at susceptible individuals and families, or at subgroups of the population, based on their genomic risk profile.The controversial nature of the political discourse concerning science and health often raises controversy, and the integration of genomics into public healthcare, research and policy might therefore be challenging. According to Brand et al (2008), the question is not whether the use of genomics in public health is dangerous, but whether excluding genomic information from public health interventions and withholding the potential of evidence-based prevention might do more harm. The next decade will provide a window of opportunity in which to prepare and educate clinicians, public health professionals, policy-makers and the public for the integration of genomics into healthcare. Brand et al (2008) argue that there is an ethical obligation to meet this challenge and make the best use of the opportunities provided by scientific progress.This, inevitably, requires a legal and regulatory framework to ensure that the benefits are made widely available to the population and, in particular, to protect consumers—today, DCGT by private companies remains a largely unregulated market. In 2008, the Committee of Ministers of the 47 Member States of the Council of Europe adopted the first international legally binding document concerning genetic testing for health purposes (Lwoff, 2009). The Additional Protocol to The Convention on Human Rights and Biomedicine about Genetic Testing for Health Purposes addresses some of the issues raised by genetic testing, from quality and clinical utility, to public information and genetic screening programmes for health purposes (Council of Europe, 2008). According to the Protocol, a health-screening programme that uses genetic tests can only be implemented if approved by the competent body, after independent evaluation of its ethical acceptability and fulfilment of specific conditions. These include the health relevance, scientific validity and effectiveness, availability of appropriate preventive or treatment measures, equitable access to the programme and availability of adequate measures to inform the population about the existence, purpose and accessibility of the screening programme, as well as the voluntary nature of participation in it.Two particular issues were discussed during the development of the Protocol: direct access to tests by individuals; and information and genetic counselling (Lwoff, 2009). The Protocol includes some debated restrictions to DCGT (Borry, 2008), to guarantee the proper interpretation of predictive test results and appropriate counselling to understand their implications. According to Article 7, with few exceptions “[a] genetic test for health purposes may only be performed under individualized medical supervision.” In order to assure quality of information and support for the patient, Article 8 states that “the person concerned shall be provided with prior appropriate information in particular on the purpose and the nature of the test, as well as the implications of its results.” Moreover, for tests for monogenic diseases, tests that aim to detect a genetic predisposition or genetic susceptibility to a disease, or tests to identify the subject as a healthy carrier of a gene responsible for a disease, appropriate genetic counselling should be available. It states that “the form and extent of this genetic counselling shall be defined according to the implications of the results of the test and their significance for the person or the members of his or her family, including possible implications concerning procreation choices.” According to this document, genetic counselling could thus go from being a “very heavy and long” procedure to a “lighter” one, but should be guaranteed in any case. The Protocol has already influenced legislation, but it will apply only in countries that have ratified it, which, so far, is only Slovenia.Companies that offer DCGTs are harbingers of change for personalized medicine. Their increasing popularity—owing not least to the ease with which their services can be obtained over the Internet—shows that the public is willing to pay for this kind of personal information. Nevertheless, healthcare systems and regulators must ensure that developments in this area benefit patients. Experience from genetic testing for neurological diseases—given their particularly severe impact on patients and their families—highlights both the current lack of proper regulation and oversight, as well as the potential health benefits that can be reaped from genetic tests.? Open in a separate windowDonato RamaniOpen in a separate windowChiara Saviane     

Ascertainment and Prevention of Genetic Disease

A genetic register system has been developed for the ascertainment and prevention of genetic disease. Its potential value is illustrated with data collected from 478 families with serious genetic disorders which had been seen during the past five years. Of these 249 were referred specifically for genetic counselling, autosomal dominant disorders accounting for the largest group of families with individuals at high risk of becoming affected. Of 717 individuals at high risk of having affected children (or carrier daughters in the case of X-linked recessive disorders), only 101 were referred specifically for counselling. Many were referred only after the birth of an affected child which might otherwise have been prevented. A genetic register system linked to practitioner, hospital, and health department records could be a valuable means of preventing genetic disease.     

Fatty Acid Diversity is Not Associated with Neutral Genetic Diversity in Native Populations of the Biodiesel Plant Jatropha curcas L.

Jatropha curcas L. (Euphorbiaceae) is a shrub native to Mexico and Central America, which produces seeds with a high oil content that can be converted to biodiesel. The genetic diversity of this plant has been widely studied, but it is not known whether the diversity of the seed oil chemical composition correlates with neutral genetic diversity. The total seed oil content, the diversity of profiles of fatty acids and phorbol esters were quantified, also, the genetic diversity obtained from simple sequence repeats was analyzed in native populations of J. curcas in Mexico. Using the fatty acids profiles, a discriminant analysis recognized three groups of individuals according to geographical origin. Bayesian assignment analysis revealed two genetic groups, while the genetic structure of the populations could not be explained by isolation‐by‐distance. Genetic and fatty acid profile data were not correlated based on Mantel test. Also, phorbol ester content and genetic diversity were not associated. Multiple linear regression analysis showed that total oil content was associated with altitude and seasonality of temperature. The content of unsaturated fatty acids was associated with altitude. Therefore, the cultivation planning of J. curcas should take into account chemical variation related to environmental factors.     

Genetic structure of Mongolic-speaking Kalmyks.

Genetic polymorphisms of blood groups ABO and RH D, serum proteins HP, TF, and GC, and red cell enzymes ACP1, PGM1, ESD, GLO1, and SOD-A have been reported for three tribes (Torguts, Derbets, and Buzavs) of the Volga's Kalmyk-Oyrats. The Kalmyks exhibit genetic markers that are characteristic of Central Asian populations, namely, high allelic frequencies for ABO*B, TF*C2, GC*IF, ESD*2, and GLO1*2, and the rare incidence of individuals with the RH-negative phenotype. Genetic distance measures reveal that close genetic affinities exist between the Derbets and Buzavs, but both populations differ significantly from the Torguts. Collectively as an ethnic group, the Kalmyks genetically resemble the contemporary Buryats of the Baikal region of southeastern Siberia and the Mongols of Mongolia. The transplantation of the Kalmyk-Oyrats from their homeland near Lake Baikal to their current residence (4500 km) near the Caspian Sea and their subsequent isolation for more than 300 years have not appreciably altered the gene frequencies from the parental populations for frequencies of standard genetic markers.     

A comparison of four methods for detecting weak genetic structure from marker data

Genetic structure is ubiquitous in wild populations and is the result of the processes of natural selection, genetic drift, mutation, and gene flow. Genetic drift and divergent selection promotes the generation of genetic structure, while gene flow homogenizes the subpopulations. The ability to detect genetic structure from marker data diminishes rapidly with a decreasing level of differentiation among subpopulations. Weak genetic structure may be unimportant over evolutionary time scales but could have important implications in ecology and conservation biology. In this paper we examine methods for detecting and quantifying weak genetic structures using simulated data. We simulated populations consisting of two putative subpopulations evolving for up to 50 generations with varying degrees of gene flow (migration), and varying amounts of information (allelic diversity). There are a number of techniques available to detect and quantify genetic structure but here we concentrate on four methods: F(ST), population assignment, relatedness, and sibship assignment. Under the simple mating system simulated here, the four methods produce qualitatively similar results. However, the assignment method performed relatively poorly when genetic structure was weak and we therefore caution against using this method when the analytical aim is to detect fine-scale patterns. Further work should examine situations with different mating systems, for example where a few individuals dominate reproductive output of the population. This study will help workers to design their experiments (e.g., sample sizes of markers and individuals), and to decide which methods are likely to be most appropriate for their particular data.     

COMMENTARY ON ZOHAR'S “PROSPECTS FOR‘GENETIC THERAPY’- CAN A PERSON BENEFIT FROM BEING ALTERED?”

In his paper on the effects of Prenatal Genetic Intervention (PGI) on personal identity, Noam Zohar comes to a conclusion about genetic makeup and the uses of gene therapy quite different from the one I reach in another piece in this issue. Zohar's argument rests on the contention that personal identity changes with alteration of the genome, following what I have identified as the "constitutive" view. To see that this is the pillar supporting the weight of his argument, consider the following. Questions of identity aside, how can it be that altering the genome of children suffering from Lesch-Nyhan syndrome or Tay-Sachs disease so that they now produce the enzyme that they formerly lacked does not benefit them? Clearly, if their identities were not changed, such individuals would in fact realize great benefit from PGI, since the devastating bad effects of the genetic flaw would be avoided. Such a change would certainly make the altered individuals better off, that is, it would benefit them. On this, Zohar and I do not disagree. Persistence of identity through such genetic change is the sticking point.     

Homo sapiens: From man to demigod. By Bernhard Rensch. ix + 228 pp., figures,bibliography, index. Columbia University Press,New York. 1972. $10.00 (cloth)

The Zuni Indians of west-central New Mexico have been relatively isolated since their foundation by an amalgamation of individuals from different southwestern cultural areas during the Regressive Pueblo period (c.1200–1350 A.D. ). Genetic analysis revealed a high frequency of blood type B in both young (0.06) and old (0.05) Zuni, but at 14 other blood group and serum protein loci, allelic frequencies including A (0.011) and Rh negative (0.001) were generally similar to those of other relatively unmixed southwestern Indian tribes. Consideration of Zuni history and demography since Spanish contact in 1540, together with genetic analyses, suggest that the high B frequency probably derives from intermixture with a small number of B, Rh positive non-Indians in the early post contact period. Genetic differentiation among four southwestern tribes, Zuni, Pima, Papago and Maricopa, was summarized by kinship analysis. Approximately 70% of the inter-tribal genetic variation could be explained by the geographic distances among these groups showing that isolation by distance has been the most important factor in determining the pattern of regional genetic differentiation.