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PubMed2005

Cystic fibrosis prenatal screening in genetic counseling practice: recommendations of the National Society of Genetic Counselors.

For over a decade, prenatal screening for cystic fibrosis (CF) has been considered a model for the integration of genetic testing into routine medical practice. Data from pilot studies and public policy discourse have led to recommendations by some professional organizations that CF screening should be offered or made available to pregnant women and their partners, and to couples planning a pregnancy. It is crucial that genetic counselors gain thorough understanding of the complexities of CF and the implications of positive test results, so that they may serve as a reliable, educated referral base and resource for health care providers and their patients. While not all pregnant women will be referred for genetic counseling prior to CF carrier testing, genetic counselors often will be asked to counsel clients after they have a positive test result, or who are found to be at increased risk. Genetic counselors can play an important role in providing accurate and current information as well as support for patients' informed decisions. These recommendations were created by a multicenter working group of genetic counselors with expertise in CF and are based on personal clinical experience, review of pertinent English language medical articles, and reports of expert committees. The recommendations should not be construed as dictating an exclusive course of management, nor does the use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care provider's professional judgment based on the clinical circumstances of a particular client.

Alleles↗

PubMed2005

Genetic basis of common diseases: the general theory of Mendelian recessive genetics.

Common diseases tend to appear sporadically, i.e., they appear in an individual who has no first or second degree relatives with the disease. Yet diseases are often associated with a slight but definite increase in risk to the children of an affected individual. This weak pattern of inheritability cannot be explained by conventional interpretations of Mendelian genetics, and it is therefore commonly held that there is "incomplete penetrance" of a gene, or that there are polygenic, or multifactorial modes of inheritance. However, such arguments are heuristic and lack predictive power. Here, we explore the possibility that "incomplete penetrance" means the existence of a second, disease-related, gene. By examining in detail a specific common condition, Parkinson's disease (PD), we show that the sporadic form of the disease can be fully explained by a compact fully penetrant genotype involving an interaction between two, and only two, genes. In this model, therefore PD is fundamentally genetic. Our digenic model is complementary to Mendelian recessive genetics, but taken together with the latter forms a complete description for recessive genetics on one chromosome. It explains the slight increase in risk to the children if one parent has sporadic PD, and makes strict predictions where both parents coincidentally have sporadic PD. These predictions were verified in two large and carefully selected kindred, where the data also argue against other genetic models, including oligogenic and polygenic schemes. Since the inheritance patterns of sporadic PD are reminiscent of what is seen in many common diseases, it is plausible that similar genetic forms could apply to other diseases. Seen in this light, diseases wash in and out of every family, so that in a sense, over time every human family is equally at risk for most diseases.

Family Health↗

PubMed2003

Genetic structure, conservation genetics and evidence of speciation by range expansion in shy and white-capped albatrosses.

Six variable microsatellite loci were used to examine genetic structuring in the closely related shy albatross (Thalassarche cauta) and white-capped albatross (T. steadi). First, levels of genetic differentiation between the species, and among three populations within each species, were analysed using amova, FST and RST. We found high levels of genetic structuring and detected many unshared alleles between the species, which provide strong evidence against any contemporary gene flow between them. Within each species, shy albatross populations were found to be genetically distinct whereas white-capped albatross populations were undifferentiated, which implies that dispersal events are much rarer in the former than in the latter. These results formed the basis for the recommendation that the three white-capped albatross populations (as a whole) and each shy albatross population be treated as separate units for conservation. Second, levels of genetic diversity and allelic patterns in shy and white-capped albatrosses were assessed for whether they support earlier mtDNA results suggesting that shy albatrosses arose through range expansion of white-capped albatrosses. All measures indicated lower genetic diversity within shy albatrosses than within white-capped albatrosses and upheld the hypothesis that shy albatrosses were founded by white-capped albatrosses.

Analysis of Variance↗

PubMed2005

Genetic variance in female condition predicts indirect genetic variance in male sexual display traits.

During sexual encounters, individuals often use signals, such as display traits, to attract mates. If individuals alter their display traits with respect to the genotype of potential mates, indirect genetic effects (IGEs) may occur in which the genes of one individual influence the phenotype of another. Although IGEs between related individuals have received much attention, their occurrence between unrelated individuals during sexual encounters has not. Here, we demonstrate that in the Australian fruit fly Drosophila serrata, males assess females by using both visual and olfactory cues, resulting in a rapid plastic response (within minutes) in male cuticular hydrocarbons (CHCs), a display trait that is an important target of mate choice. Several CHCs in males exhibited significant IGEs, and IGEs were inducible on both males reared in the laboratory and on field-caught individuals. A vector describing genetic variance in multiple CHCs in females was found to be almost identical to a vector describing indirect genetic variance in male CHCs, suggesting that males might assess female CHCs during courtship. This vector displayed contributions from all female CHCs in the same direction and of similar magnitude, suggesting that female condition may be the underlying casual trait that males are assessing. Consistent with this interpretation, when measured directly in a separate experiment, genetic variance in female condition accounted for 19.8% of the indirect genetic variance in male CHCs. These indirect genetic effects have the potential to alter the response to selection of male sexual display traits.

Animals↗

PubMed2003

Analysis of genetic diversity in red clover (Trifolium pratense L.) breeding populations as revealed by RAPD genetic markers.

Red clover is an important forage legume species for temperate regions and very little is known about the genetic organization of its breeding populations. We used random amplified polymorphic DNA (RAPD) genetic markers to address the genetic diversity and the distribution of variation in 20 breeding populations and cultivars from Chile, Argentina, Uruguay, and Switzerland. Genetic distances were calculated for all possible pairwise combinations. A high level of polymorphism was found and the proportion of polymorphic loci across populations was 74.2%. A population derived from a non-certified seedlot displayed a higher proportion of polymorphic loci than its respective certified seedlot. Gene diversity values and population genetics parameters suggest that the populations analyzed are diverse. An analysis of molecular variance (AMOVA) revealed that the largest proportion of variation (80.4%) resides at the within population level. RAPD markers are a useful tool for red clover breeding programs. A dendrogram based on genetic distances divided the breeding populations analyzed into three distinct groups. The amount and partition of diversity observed can be of value in identifying the populations that parents of synthetic cultivars are derived from and to exploit the variation available in the populations analyzed.

Analysis of Variance↗

PubMed2001

A genetic engineering approach to genetic algorithms.

We present an extension to the standard genetic algorithm (GA), which is based on concepts of genetic engineering. The motivation is to discover useful and harmful genetic materials and then execute an evolutionary process in such a way that the population becomes increasingly composed of useful genetic material and increasingly free of the harmful genetic material. Compared to the standard GA, it provides some computational advantages as well as a tool for automatic generation of hierarchical genetic representations specifically tailored to suit certain classes of problems.

Algorithms↗

PubMed2006

Genetic modification and genetic determinism.

In this article we examine four objections to the genetic modification of human beings: the freedom argument, the giftedness argument, the authenticity argument, and the uniqueness argument. We then demonstrate that each of these arguments against genetic modification assumes a strong version of genetic determinism. Since these strong deterministic assumptions are false, the arguments against genetic modification, which assume and depend upon these assumptions, are therefore unsound. Serious discussion of the morality of genetic modification, and the development of sound science policy, should be driven by arguments that address the actual consequences of genetic modification for individuals and society, not by ones propped up by false or misleading biological assumptions.

Genetic Determinism↗

PubMed1993

Effect of selection for maternal and direct genetic effects on genetic improvement of litter size in swine.

Optimum weighting ratios of maternal:direct EBV for litter size using an animal model were examined to achieve maximum genetic improvement (direct plus maternal response). Stochastic simulation of a 120-sow herd over a 10-yr period of selection was used (20 replicates). Directional selection was based on a merit function of maternal and direct EBV for first-parity litter size. Optimum weighting ratios for maternal to direct EBV in pure- and crossbreeding schemes with different genetic correlations between maternal and direct effects were obtained. Genetic gain in maternal and direct effects was more sensitive to change in weighting ratios of maternal to direct estimates of breeding values under an animal model than earlier theoretical studies showed for selection index. In the purebreeding scheme, the weighting ratios of maternal:direct effects of 1:1, 1.25:1, and -.5:1 resulted in the highest overall response of 3.11, 1.73, and .69 pigs after 10 yr of selection with genetic correlations between maternal and direct effects of 0, -.5, and -.9, respectively. In the crossbreeding scheme with a male dam line selected for direct effects only and a female dam line selected for an optimum weighting ratio of maternal and direct effects the overall response was always higher with 3.19, 1.89, and 1.31 pigs/10 yr for the genetic correlations 0, -.5, and -.9, respectively, than in the purebreeding scheme. With a large negative correlation between maternal and direct effects a meaningful overall response of litter size was achieved only in the crossbreeding scheme. The effect of negative weighting of maternal effects to increase direct response with a large negative correlation between maternal and direct effects was also examined as well as the influence of weighting ratios on accuracy of evaluation, additive genetic variance, prediction error variance, and correlation between maternal and direct EBV.

Animals↗

PubMed1998

Genetic variation and prediction of additive and nonadditive genetic effects for six carcass traits in an Angus-Brahman multibreed herd.

Estimates of covariances and sire expected progeny differences of additive and nonadditive genetic effects for six carcass traits were obtained using records from 486 straightbred and crossbred steers from 121 sires born between 1989 and 1995 in the Angus-Brahman multibreed herd of the University of Florida. Steers were slaughtered at a similar carcass composition end point. Covariances were estimated by REML procedures, using a generalized expectation-maximization algorithm applied to multibreed populations. Straightbred and crossbred estimates of heritabilities and additive genetic correlations were within ranges found in the literature for steers slaughtered on an age- or weight-constant basis for hot carcass weight, longissimus muscle area, and shear force but equal to or less than the lower bound of these ranges for fat-related traits. Maximum values of interactibilities (i.e., ratios of nonadditive variances to phenotypic variances in the F1) and nonadditive genetic correlations were smaller than heritabilities and additive genetic correlations in straightbreds and crossbred groups. Sire additive and total direct genetic predictions for longissimus muscle area, marbling, and shear force tended to decrease with the fraction of Brahman alleles, whereas those for hot carcass weight and fat thickness over the longissimus were higher, and those for kidney fat were lower in straightbreds and F1 than in other crossbred groups. Nonadditive genetic predictions were similar across sire groups of all Angus and Brahman fractions. These results suggest that slaughtering steers on a similar carcass composition basis reduces variability of fat-related traits while retaining variability for non-fat-related traits comparable to slaughtering steers on a similar age or weight basis. Selection for carcass traits within desirable (narrow) ranges and slaughter of steers at similar compositional end point seems to be a good combination to help produce meat products of consistent quality.

Abattoirs↗

PubMed2002

Medical genetics: 3. An approach to the adult with a genetic disorder.

Many genetic disorders do not manifest themselves until the adult years. Such disorders often involve multiple genetic factors interacting with multiple environmental factors, over time, to produce a phenotype. This paper reviews the modes of inheritance of genetic disorders and describes the types of genetic testing that are currently available. It offers clues that should lead physicians to suspect that an adult patient might have a genetic disorder and raises issues that should be considered in counselling the patient about genetic testing. Resources for patients and their family physicians are also discussed.

Adult↗

PubMed2003

[Genetic counseling and genetic services].

Advances in knowledge about the genetic basis of disease have lead to an increasing demand for and expectation of genetic counselling and genetic services. This presents a new challenge to the health care system, as well as a need for professional education and public dialogue. In this review the current provision of genetic counselling and services is described, especially with the focus on the process of counselling and the persons presenting for counselling. Genetic counselling is seen as an information process and the scenarios for decision-making are discussed. The future development of genetic services should be developed within an ethical framework and the importance of quality assessment is underlined.

Decision Making↗

PubMed2003

Genetics in dental practice: social and ethical issues surrounding genetic testing.

It is evident that human genetic variation is associated with many if not all human diseases including the more prevalent chronic diseases. As a result, genetics is becoming integrated into health care in all medical specialties, including oral medicine and its specialties. At the level of public health, genetic information will become increasingly important in research, policy, and program development. As application of genome technologies moves from the research laboratory to the clinical setting, a complex array of challenges will face dental clinicians in their efforts to use genetic information to improve health care and prevent disease on an individual, family, and community level. The broader social, ethical, and legal implications raised by the clinical use of genomic information have not received the same attention as did recent gene identification aspects of the Human Genome Project. The goal of this review is to foster attention and dialogue within the dental community of the ethical and social issues emerging from the availability of genetic information. Specific areas addressed include genetic testing, confidentiality, discrimination, informed consent, risk communication, and professional education.

Confidentiality↗

PubMedDate not supplied

Genetic fatalism and social policy: the implications of behavior genetics research.

Recent advances in molecular genetics methods have provided new means of determining the genetic bases of human behavioral traits. The impetus for the use of these approaches for specific behaviors depends, in large part, on previous familial studies on inheritance of such traits. In the past, a finding of a genetic basis for a trait was often accompanied with the idea that that trait is unchangeable. We discuss the definition of "genetic trait" and heritability and examine the relationship between these concepts and the malleability of traits for both molecular and nonmolecular approaches to behavioral genetics. We argue that the malleability of traits is as much a social and political question as it is a biological one and that whether or not a trait is genetic has little relevance to questions concerning determinism, free will, and individual responsibility for actions. We conclude by noting that "scientific objectivity" should not be used to conceal the social perspectives that underlie proposals regarding social change.

Female↗

PubMed1997

Etiology, natural history, management and molecular genetics of hereditary nonpolyposis colorectal cancer (Lynch syndromes): genetic counseling implications.

We estimate that 5-10% of virtually all forms of cancer are due to a primary hereditary etiology. However, a hereditary cancer diagnosis is often missed because the family history of cancer is given short shrift in medical practice. Hereditary nonpolyposis colorectal cancer (HNPCC) certainly fits this estimate, although some studies suggest that a minimum of 2% with a range as high as 10% of the total colorectal cancer burden is due to HNPCC. Mutations in one of the four mismatch repair genes, i.e., hMSH2, hMLH1, hPMS1, and hPMS2, account for about 70% of HNPCC kindreds. Other germ-line mutations are likely to be identified to account for the remainder of HNPCC patients. By far the most common HNPCC mutations involve hMSH2 and hMLH1, with hPMS1 and hPMS2 accounting for only about 3% of such families. Prior to these molecular genetic discoveries, the genetic counselor could only provide the patient with an estimate of a 50% likelihood of manifesting HNPCC based on the counselee having one or more first-degree relatives manifesting syndrome cancers in their direct genetic lineage. Because DNA testing has become available in families with known mutations, we have provided pretest group education in the form of a family information service with intensive education about the natural history, genetic risk, surveillance, and options for management of HNPCC, as well as discussion of the potential for fear, anxiety, apprehension, and insurance or employer discrimination that might impact on this DNA testing. Following informed consent, these relatives were then counseled on a one-to-one basis. Using DNA-based genetic counseling involving hMSH2 or hMLH1, we have provided this service to four extended HNPCC kindreds. Details of this genetic counseling experience on these four kindreds will be discussed.

Adaptor Proteins, Signal Transducing↗

PubMed1997

[Clinical genetics in The Netherlands. II. Genetic counseling and prenatal diagnosis].

The main feature of clinical genetics is the involvement of close relatives in the diagnostics of a hereditary disorder, and the possible consequences of the findings for future generations. Complex genetic counseling is required in cases with different, possibly hereditary disorders or congenital anomalies in the family or by a syndrome with variable risks of recurrence, depending on the exact nature of the disorder; also the difficult, often emotionally charged choices with which counselees are faced demands the expertise of a clinical genetic centre. Results of follow-up studies after genetic counseling show that experience with a handicap or disease in the own environment and the presence of healthy issue are the main determinants for the decision about reproduction of persons with an enhanced genetic risk who request counseling. Because of the great variety in perception of risks and of the severity of a disorder, and because of the marked clinical heterogeneity, rigid legislation should be avoided in the field of prenatal diagnosis. In the future, the training of the clinical geneticist has to be adapted to the rapid progress in human genetics. Increasingly, the clinical geneticist will function in collaboration with other disciplines such as oncology, obstetrics and gynaecology, paediatrics and neurology; in connection with family testing and counseling, there will also be more collaboration with primary health care.

Adult↗

PubMed1995

Genetic testing and insurance. The Ad Hoc Committee on Genetic Testing/Insurance Issues.

The rapid expansion of opportunities for genetic testing has been accompanied by complex questions about the appropriate relationships between providers, patients, and insurers. Some of these questions involve large public-policy decisions, such as whether the government should guarantee access to health care for all citizens. Universal access to health care, without regard to past, present, or future risk of disease, could eliminate risk-oriented underwriting in health-care coverage. A positive response to that question will ameliorate other problems. Until universal access is reality, genetic testing and genetic diagnosis will raise important issues for the practicing geneticist. How much does a client need to know about insurance implications before consenting to a genetic test? Should patients be counseled to purchase insurance before being tested? Should genetic information be excluded from medical records before their release to insurance companies for routine reimbursements or underwriting? What are the ethical and legal responsibilities of the geneticist?

Confidentiality↗

PubMed2005

Chemical genetics and orphan genetic diseases.

Many orphan diseases have been identified that individually affect small numbers of patients but cumulatively affect approximately 6%-10% of the European and United States populations. Human genetics has become increasingly effective at identifying genetic defects underlying such orphan genetic diseases, but little progress has been made toward understanding the causal molecular pathologies and creating targeted therapies. Chemical genetics, positioned at the interface of chemistry and genetics, can be used for elucidation of molecular mechanisms underlying diseases and for drug discovery. This review discusses recent advances in chemical genetics and how small-molecule tools can be used to study and ultimately treat orphan genetic diseases. We focus here on a case study involving spinal muscular atrophy, a pediatric neurodegenerative disease caused by homozygous deletion of the SMN1 (survival of motor neuron 1) gene.

Drug Design↗

PubMedDate not supplied

Does genetic variance for cognitive abilities account for genetic variance in educational achievement and occupational status? A study of twins reared apart and twins reared together.

Studies of brothers and twins have shown that about 50 per cent of the variance in educational achievement and 40 per cent of the variance in occupational status reflects between-family variance. About half of the between-family variance for educational achievement and even more for occupational status is due to genetic effects and the remainder is due to sharing the same environment. With data on 35 pairs of male twins reared apart and 56 pairs reared together we investigated the extent to which genetic variance in SES can be attributed to genetic variance for cognitive abilities. For both educational achievement and occupational status there was significant genetic variance both in common with and independent of genetic variance for cognitive abilities. Thus, there are genetic effects contributing to familial similarity for SES that are not the same as those of importance for cognitive abilities. Candidate traits that may account for this remaining genetic variance in SES are personality, interests, or talents not represented in standard cognitive tests.

Achievement↗