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PubMed2003

Allelic variation and genetic linkage of avian microsatellites in a new turkey population for genetic mapping.

Efforts to build a comprehensive genetic linkage map for the turkey (Meleagris gallopavo) have focused on development of genetic markers and experimental resource families. In this study, PCR amplification was attempted for 772 microsatellite markers that had been previously developed for three avian species (chicken, quail and turkey). Allelic polymorphism at 410 markers (53.1% of total examined) was determined by genotyping ten individuals (six F1 parents and four grandparents) in a new resource population specifically developed for genetic linkage mapping. Of these 410 markers, 109 (26.6%) were polymorphic in the tested individuals, with an average of 2.3 alleles per marker. Higher levels of polymorphism were found for the turkey-specific markers (61.1%) than for the chicken (22.7%) or quail-specific markers (33.3%). To test the fidelity of the matings, demonstrate the power of these families for linkage analysis, and determine genetic linkage relationships, 86 polymorphic markers were genotyped for up to 224 birds including founder grandparents, parents and F2 progeny. Linkage relationships for many of the chicken markers elucidated in the turkey were comparable to those observed in the chicken. These data demonstrate that the new UMN/NTBF resource population will provide a solid foundation for constructing a comparative genetic map of the turkey.

Alleles↗

PubMed2004

Defining the phenotype in human genetic studies: forward genetics and reverse phenotyping.

The definition of phenotypes for genetic study is a challenging endeavor. Just as we apply strict quality standards to genotype data, we should expect that phenotypes meet consistently high standards of reproducibility and validity. The methods for achieving accurate phenotype assignment in the research setting--the 'research diagnosis'--are different from the methods used in clinical diagnosis in the patient care setting. We evaluate some of the main challenges of phenotype definition in human genetics, and begin to outline a set of standards to which phenotypes used in genetics studies may aspire with the goal of increasing the quality and reproducibility of linkage and association studies. Revisiting the traditional phenotype definitions through a focus on familial components and heritable endophenotypes is a time-honored approach. Reverse phenotyping, where phenotypes are refined based on genetic marker data, may be a promising new approach. The stakes are high, since the success of gene mapping in genetically complex disorders hinges on the ability to delineate the target phenotype with accuracy and precision.

Chromosome Mapping↗

PubMed2003

Duty to warn at-risk relatives for genetic disease: genetic counselors' clinical experience.

When a patient refuses to inform relatives of their risk for genetic disease, the genetic healthcare professional is faced with conflicting ethical obligations. On one side of the issue is the obligation to respect and protect patients' right to privacy. On the other side is the obligation to prevent harm and promote the welfare of the family members, which suggests a responsibility to warn at-risk relatives, even without the patient's consent. In an effort to examine the actual clinical impact of this issue, we conducted a pilot study that explored genetic counselors' experience with this conflict. A survey was developed and made available to members of the National Society of Genetic Counselors. Questions were either multiple-choice responses or open-ended. Almost half of respondents (119/259; 46%) had had a patient refuse to notify an at-risk relative. The most commonly cited reasons for refusal were estranged family relationships, altering family dynamics, insurance discrimination, and employment discrimination, respectively. Of these 119 counselors, 24 (21%) reported that they seriously considered warning the at-risk relatives without patient consent, and one actually did disclose. Three factors consistently made the counselors less likely to disclose: their patient's potential emotional reaction, the relationship between the relative and patient, and the chance that the relative could be aware of the disease by another means. These results suggest that while the conflict is often encountered in clinical practice, it is rare that the situation remains unresolved to the extent that genetic counselors actually consider warning at-risk relatives. However, when the situation was encountered, the counselors in this study reported a lower rate of disclosure without consent than would have been anticipated based on previous studies that used hypothetical situations. It may be that counselors do not recognize a duty to warn at-risk relatives as integral to their role and professional obligations.

Data Collection↗

PubMed2025

Genetics first approach: Expanding the utility of genetic testing by nongeneticist physicians.

PURPOSE: The increasing demand for genetic testing and a global shortage of geneticists has significantly strained health care systems worldwide. This highlighted the need for new strategies aiming to increase testing accessibility, reduce wait times, and enhance patient care quality. METHODS: We implemented a 4-step program, "Genetics First," to empower nongeneticist physicians (NGPs) to play an active role in the process of genetic consultation and testing. The steps included (1) establishing criteria to identify suitable clinical domains, (2) selecting clinical indications within the domain through expert panel review, (3) designing tailored education and workflows for NGPs across indications, and (4) monitoring test outcomes and providing further support for complex cases. Test outcomes were compared between NGPs and clinical geneticists. RESULTS: Endocrinology was selected as the first domain, with 114 endocrinologists who completed the program. During the study, 260 gene panels were performed for monogenic diabetes, with NGPs initiating 68% of tests, leading to a 107% increase in referrals. The diagnostic yield was 30%, with no significant difference between NGP- and clinical geneticist-initiated tests. CONCLUSION: This study demonstrates the feasibility and impact of involving NGPs in genetic testing, offering a paradigm shift that could expand access to genetic testing and improve patients' care and clinical outcomes.

Humans↗

PubMed2002

Genetic testing for disease susceptibilities: consequences for genetic counseling.

The role of genetic counseling in future testing for inherited susceptibilities for common diseases is debated. Currently, genetic testing, ideally supported by genetic counseling, is most often used to modify the assessment of genetic risk of Mendelian-inherited disease in high-risk individuals for the purpose of personal decision-making. By contrast, it is anticipated that genetic testing will be used to identify increased disease susceptibility in low-risk individuals for the purpose of instituting medical or lifestyle interventions to modify risk for future disease.

Genetic Counseling↗

PubMed2005

Genetic diversity in german and European populations: looking for substructures and genetic patterns.

A classical case-control study is a powerful and cost-efficient approach to detect association of genetic markers with complex disease phenotypes. However, only a small fraction of significant association results has been replicated by other studies. Undetected genetic substructures in the population may be one of the reasons for spurious or biased results. The German "Genomic Control" study aims at detecting genetic differentiation between one Southern German population, represented by the KORA study (KORA Survey S4 (1999/2001)), and two Northern German populations (SHIP, Greifswald, and POPGEN, Schleswig-Holstein). Relevant population-substructures will be assessed, as well as their influence on case-control studies. Since KORA samples are used as controls for different German genetic association studies, the knowledge gained through this Genomic Control project will influence the planning of further genetic association studies. A second project, the European LD study, deals with the detection and comparison of linkage disequilibrium (LD) patterns in the human genome for eight distinct European populations. In general, a conservation of LD patterns across European samples can be observed for most gene regions. However, there are chromosomal regions with variable LD structure which may have implications on the fine-mapping of genes in different populations.

Adult↗

PubMed2005

The effect of preventability and severity levels of a genetic disorder on desire to communicate genetic testing information to family members.

This study examined the impact of severity and preventability of a genetic disorder on belief that genetic test results should be shared with family members, desire to be tested, and opinions about physician?s role in sharing information. Participants were 359 undergraduate students who received one of four descriptions of a fictitious genetic disorder called hemocythemia (i.e., factorial combination of high versus low disease preventability and high versus low disease severity). Logistic regression analyses indicated that disease severity and preventability did not influence agreement that genetic information should be shared with family members, interest in being tested for the disorder, or agreement that physicians should share genetic information without permission. Those who read about the disorder as preventable were more likely to agree that their family members should be tested for the disorder (odds ratio [OR] = 1.82, p < 0.05). Females, African Americans, and those of other races were more likely to agree that they would want their family members tested for hemocythemia than males or European Americans (p < 0.05). Describing the disorder as preventable minimized the effect of the severity manipulation on perception of disease severity (p < 0.05). Understanding a disorder to be preventable may increase encouragement of family members to be tested and affect perceived seriousness of the condition.

Adult↗

PubMed2006

New roles for model genetic organisms in understanding and treating human disease: report from the 2006 Genetics Society of America meeting.

Fundamental biological knowledge and the technology to acquire it have been immeasurably advanced by past efforts to understand and manipulate the genomes of model organisms. Has the utility of bacteria, yeast, worms, flies, mice, plants, and other models now peaked and are humans poised to become the model organism of the future? The Genetics Society of America recently convened its 2006 meeting entitled "Genetic Analysis: Model Organisms to Human Biology" to examine the future role of genetic research. (Because of time limitations, the meeting was unable to cover the substantial contributions and future potential of research on model prokaryotic organisms.) In fact, the potential of model-organism-based studies has grown substantially in recent years. The genomics revolution has revealed an underlying unity between the cells and tissues of eukaryotic organisms from yeast to humans. No uniquely human biological mechanisms have yet come to light. This common evolutionary heritage makes it possible to use genetically tractable organisms to model important aspects of human medical disorders such as cancer, birth defects, neurological dysfunction, reproductive failure, malnutrition, and aging in systems amenable to rapid and powerful experimentation. Applying model systems in this way will allow us to identify common genes, proteins, and processes that underlie human medical conditions. It will allow us to systematically decipher the gene-gene and gene-environment interactions that influence complex multigenic disorders. Above all, disease models have the potential to address a growing gap between our ability to collect human genetic data and to productively interpret and apply it. If model organism research is supported with these goals in mind, we can look forward to diagnosing and treating human disease using information from multiple systems and to a medical science built on the unified history of life on earth.

Animals↗

PubMed2003

Between acculturation and ambivalence: knowledge of genetics and attitudes towards genetic testing in a consanguineous bedouin community.

UNLABELLED: The Bedouins of the Negev (Southern part of Israel) are a community at increased risk for genetic diseases and congenital anomalies as a result of frequent consanguinity (particularly patrilateral parallel-cousin marriage) and underutilization of prenatal genetic tests due to a Muslim ban on abortion. OBJECTIVE: To assess the knowledge and attitudes of Bedouin schoolchildren and their teachers towards a community-based, premarital carrier-matching program aimed at reducing the prevalence at birth of genetic diseases. METHODS: A questionnaire was presented to 61 teachers and 40 schoolchildren as part of guided interaction in small groups, conducted in Bedouin schools between 1999 and 2001. RESULTS: Susceptibility as well as knowledge of genetics were found to correlate with a positive attitude towards the genetics program among both teachers and pupils. However, pupils had a lower knowledge index as compared to teachers, and their attitudes were slightly less positive. CONCLUSION: The difference between teachers and pupils is discussed in the context of the latter's acculturation, which contradicts tradition and parental authority and can generate ambivalence. Attitudes are further discussed in the context of the Health Belief Model and the complex interplay of tradition, Islam, cousin marriage and biomedicine.

Acculturation↗

PubMed2005

A sarcoidosis genetic linkage consortium: the sarcoidosis genetic analysis (SAGA) study.

BACKGROUND: Sarcoidosis, a systemic granulomatous disease of unknown etiology, likely results from an environmental insult in a genetically susceptible host. In the United States of America, African Americans have a higher sarcoidosis incidence and suffer greater morbidity than Caucasians. METHODS: A sarcoidosis genetic linkage study consortium was established to recruit African-American affected sib pair (ASP) families to identify chromosomal regions that may harbor sarcoidosis susceptibility genes and to determine if environmental factors modify any genetic effects. RESULTS: We successfully met our goal of enrolling 359 ASPs using a multifaceted recruitment approach. In the total 559 sib pairs that were enrolled, genetic analyses revealed incorrectly specified relationships that required reclassification or removal from the analysis dataset of 10.4% of reported full and 1.4% of reported half sib pairs. The final study sample comprised 415 full and 104 half sib pairs with complete data. This included 338 ASPs. Within sib pairs, affection status was not associated with sex. Only 15 per cent of the 229 families had three or more affected sibs, but they contributed 42 per cent of the ASP total. CONCLUSIONS: The SAGA study experience should provide useful lessons and information to serve others in conducting genetic studies of complex diseases in African-American families.

Black or African American↗

PubMed2005

[The Human Genome Project, genetic viability and genetic epidemiology].

The goal of the Human Genome Project to elucidate the complete sequence of the human genome has been achieved. The aims of the "post-genome" era are explaining the genetic information, characterisation of functional elements encoded in the human genome and mapping the human genetic variability as well. Two unrelated human beings also share 99.9% of their genomic sequence. The difference of 0.1% is the result of genetic polymorphisms: single nucleotide polymorphisms, repetitive sequences and insertion/deletion. The genetic differences, coupled with environmental exposures will determine the phenotypic variation we observe in health or disease. The disease-causing genetic variants can be identified by linkage analysis or association studies. The knowledge of human genome and application of multiple biomarkers will improve our ability to identify individuals at risk, so that preventive interventions can be applied, earlier diagnosis can be made and treatment can be optimized.

Early Diagnosis↗

PubMed1991

Genetic factors in neurotoxicology and neuropharmacology: a critical evaluation of the use of genetics as a research tool.

Animals have evolved a detoxication system to enable them to survive in a hostile chemical environment in which foods contain many non-nutrient chemicals. Detoxication depends on enzymes which are often genetically polymorphic. As a result, inter-individual variation is common, and in humans several Mendelian loci have been identified. However, most variation in response is probably due to the action of several genes. Genetic variation in response to the neurotoxin MPTP and to chemically and physically-induced seizures is reviewed. In the former case, differences between pigmented and white mouse strains have been noted which are consistent with the hypothesis that humans are more sensitive than mice or rats because of the presence of melanin in human brains. However, variation in sensitivity probably also depends on other genes. In the case of audiogenic seizures, a single locus has been identified and mapped, but its relationship with seizures induced by other agents is not clear. Genetic variation in response to alcohol is also discussed. The failure of most toxicologists to consider genetic variation as a potentially confounding variable, and as a powerful research tool, is discussed critically in relation to non-repeatability of research on the neurotoxic effects of lead, and in relation to the genetic variation in MPTP, seizures, and alcohol response already noted. It seems clear that genetic methods provide a powerful research tool which is largely being ignored by toxicologists.

Animals↗

PubMed2005

Genetic characterisation of dough rheological properties in a wheat doubled haploid population: additive genetic effects and epistatic interactions.

Doubled haploid lines (n = 160) from a cross between wheat cultivars 'Cranbrook' (high dough extensibility) and 'Halberd' (low dough extensibility) were grown at three Australian locations. The parents differ at all high- and low-molecular-weight glutenin loci. Dough rheological parameters were measured using small-scale testing procedures, and quantitative trait locus (QTL) mapping procedures were carried out using an existing well-saturated genetic linkage map for this cross. Genetic parameters were estimated using three software packages: QTLCartographer, Epistat and Genstat. Results indicated that environmental factors are a major determinant of dough extensibility across the three trial sites, whereas genotypic factors are the major determinants of dough strength. Composite interval mapping analysis across the 21 linkage groups revealed that as expected, the main additive QTLs for dough rheological properties are located at the high- and low-molecular-weight glutenin loci. A new QTL on chromosome 5A for M-extensibility (a mixograph-estimated measure of extensibility) was detected. Analysis of epistatic interactions revealed that there were significant conditional epistatic interactions related with the additive effects of glutenin loci on dough rheological properties. Therefore, the additive genetic effects of glutenins on dough rheological properties are conditional upon the genetic background of the wheat line. The molecular basis of the interactions with the glutenin loci may be via proteins that modify or alter the gluten protein matrix or variations in the expression level of the glutenin genes. Reverse-phase high performance liquid chromatography analysis of the molar number of individual glutenin subunits across the population showed that certain conditional epistases resulted in increased expression of the affected glutenin. The epistatic interactions detected in this study provide a possible explanation of the variable genetic effects of some glutenins on quality attributes in different genetic backgrounds and provide essential information for the accurate prediction of glutenin related variance in marker-assisted wheat breeding.

Alleles↗

PubMed2005

Assessment of the use and feasibility of video to supplement the genetic counseling process: a cancer genetic counseling perspective.

Cancer genetic counselors use a variety of teaching modalities for patient education. This survey of cancer genetic counselors assessed their use of educational videos and their recommendations for content of future videos. Thirty percent of respondents use videos for patient education. Cited benefits included reinforcement of information for clients and increased counselor efficiency. Of the 70% who do not use videos, predominant barriers included the perceived lack of an appropriate video, lack of space and/or equipment, and concern that videos are impersonal. Most respondents desired a video that is representative of the genetic counseling session, but emphasized the importance of using broad information. Content considered critical included the pros and cons of genetic testing, associated psychosocial implications, and genetic discrimination. The results of this exploratory study provide data relevant for the development of a cancer genetics video for patient education, and suggestions are made based on aspects of information processing and communication theories.

Adult↗

PubMedDate not supplied

Genetic models for the natural history of smoking: evidence for a genetic influence on smoking persistence.

We reanalyze data from the 1981 mailed questionnaire survey of the Australian twin register, to test for a genetic effect on smoking persistence (whether or not a smoker quits smoking). In the young cohort, aged 18-30 years, there are too few ex-smokers to permit resolution of genetic and non-genetic models. In the older cohort, we find a significant and substantial genetic effect on smoking persistence, accounting for 53% of the variance. This genetic effect on smoking persistence is independent of genetic effects on smoking initiation.

Adolescent↗

PubMed2006

Genetic analysis of the diabetes-prone C57BLKS/J mouse strain reveals genetic contribution from multiple strains.

The C57BLKS/J (BKS) inbred mouse strain is a widely used animal model of type 2 diabetes. In the presence of the diabetes (db) mutation, obese BKS-db mice develop severe diabetes. Genetic studies of diabetes-susceptibility in this strain are facilitated by the fact that BKS is a genetic composite between the diabetes-resistant C57BL/6J (B6) and susceptible DBA/2J (DBA) strains. On this basis, it has been hypothesized that diabetes-susceptibility in BKS is conferred by DBA-derived alleles. However, recent studies revealed non-B6/non-DBA genetic material in BKS. To identify the origin of this genetic component, we generated a genomic map of BKS using 537 microsatellite markers. Our results demonstrate that, in addition to B6 and DBA, BKS contains alleles from at least three other strains, including 129, C57BL/10 and an unidentified mouse strain. We also analyzed two congenic strains, B6-db and BKS-db, which are widely used for the genetic mapping of diabetes-susceptibility loci. We identified several donor-derived genomic regions introduced during the generation of these congenic strains. In summary, our study reveals novel aspects of the genetic fine-structure of BKS and related strains and facilitates the identification of diabetes-susceptibility loci in this mouse model.

Alleles↗

PubMed2005

DNA-based genetic testing is rising steeply in a national health care system with open access to services: a survey of genetic test use in Germany, 1996-2002.

The extent to which the fast-growing body of genetic knowledge is transferred into everyday clinical practice has nowhere been assessed in a systematic way. Available quantitative analyses of DNA-based genetic test provision and uptake rates are all concerned with specific test programs. The German health-care system is ideally suited for a more general approach, because it is highly flexible regarding access to services, thus permitting quick adjustments to sudden changes in particular subfields of medicine such as genetic testing. We have measured the amount of genetic service provision in Germany between 1996 and 2002 by making use of the central database of the German national health-care system and by inquiring with private health insurance. We can document a three-fold increase of DNA-based testing in the time period 1996-2002, whereas cytogenetic analyses and genetic counseling have remained constant. The growing body of genetic knowledge does indeed seem to be transferred into medical practice at an increasing rate, and the uptake rates are largely in proportion to test offers. DNA-based testing appears to be focussed on disease-associated germ-line alterations.

DNA↗

PubMed1995

Analysis of conditional genetic effects and variance components in developmental genetics.

A genetic model with additive-dominance effects and genotype x environment interactions is presented for quantitative traits with time-dependent measures. The genetic model for phenotypic means at time t conditional on phenotypic means measured at previous time (t-1) is defined. Statistical methods are proposed for analyzing conditional genetic effects and conditional genetic variance components. Conditional variances can be estimated by minimum norm quadratic unbiased estimation (MINQUE) method. An adjusted unbiased prediction (AUP) procedure is suggested for predicting conditional genetic effects. A worked example from cotton fruiting data is given for comparison of unconditional and conditional genetic variances and additive effects.

Gossypium↗