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PubMed2006

Genetic diversity and variety composition of cassava on small-scale farms in Uganda: an interdisciplinary study using genetic markers and farmer interviews.

Cassava is a tropical crop and grown for its tuberous starchy roots. In Africa it is mainly cultivated by small-scale farmers who observe, select and name their cassava varieties based on morphology, food, social and economic interest. Here we have used an interdisciplinary approach involving farmer interviews, genetic markers and morphological descriptors to study the composition of cassava varieties on small-scale farms in 11 villages located in three districts in Uganda, the genetic structure within and between these varieties and their morphology. The composition of local, newly introduced and improved varieties differed widely between villages and districts. The Ugandan farmers in our study seemed to adopt improved varieties to a greater extent when there was a nearby market, prevalence of disease epidemics and good extension service. We found considerable genetic variation both within and between cassava varieties though the variation was larger between varieties. However, most local and improved varieties showed predominating genotypes at many loci. Accessions of commonly grown varieties meeting farmers' preferences could therefore be selected and implemented in future breeding programmes involving development, dissemination and adoption. The like-named varieties in different villages were genetically similar, demonstrating farmers' ability to differentiate and maintain the same variety over large areas. However, some varieties with different names in different villages showed both genetic and morphological similarity, suggesting that farmers may rename plants when they are introduced into their fields. The large differences found in variety and genetic composition between villages and districts in Uganda may be a result of the diverse needs and growing conditions characteristic for traditional farming system. This suggests that efforts to conserve and increase the genetic diversity in farmers' fields will require policies tailored to each area.

Africa↗

PubMed2025

The development and usability of 'The Genetics Navigator': a digital solution for adult and paediatric clinical genetics services.

Clinical genetic services address diverse genetic testing needs, but there is no comprehensive digital solution to meet this variety. We aimed to develop and test the usability of the Genetics Navigator (GN), a platform designed to enhance genetic services for paediatric and adult patients. The GN prototype was created with input from a patient and clinician advisory board, informed by prior research. Usability testing involved genetics patients (N = 14), parents of paediatric patients (N = 4), and the general public (N = 10). Participants provided feedback using the 'think aloud' method when using the platform. We used the System Usability Scale (SUS) for quantitative evaluation. Qualitative data were coded by platform section, item, and identified key areas for improvement. Building on the Genetics Adviser platform, we added video and written content for various genetic conditions and patient groups, including pre-test education, counselling, decision support, history collection, post-test result disclosure, and management. Key feedback during rounds of usability testing emphasized the need for a supportive design, seamless workflow, and engaging experience of the tool. The tool was modified to reflect the feedback, and the GN achieved an average SUS score of 87.7 ± 10.9 (N = 28), indicating above-average usability. Future research will evaluate its clinical and cost-effectiveness in a randomized trial.

Humans↗

PubMed2003

Genetic polymorphism and trade-offs in the early life-history strategy of the Pacific oyster, Crassostrea gigas (Thunberg, 1795): a quantitative genetic study.

We investigated genetic variability and genetic correlations in early life-history traits of Crassostrea gigas. Larval survival, larval development rate, size at settlement and metamorphosis success were found to be substantially heritable, whereas larval growth rate and juvenile traits were not. We identified a strong positive genetic correlation between larval development rate and size at settlement, and argue that selection could optimize both age and size at settlement. However, trade-offs, resulting in costs of metamorphosing early and large, were suggested by negative genetic correlations or covariances between larval development rate/size at settlement and both metamorphosis success and juvenile survival. Moreover, size advantage at settlement disappeared with time during the juvenile stage. Finally, we observed no genetic correlations between larval and juvenile stages, implying genetic independence of life-history traits between life-stages. We suggest two possible scenarios for the maintenance of genetic polymorphism in the early life-history strategy of C. gigas.

Animals↗

PubMed1990

[Ethnic genetics: relation between adaptive and neutral genetic differentiation of an ethnos].

It is very important to be able to distinguish between selectively significant genetic variability and selectively-neutral one for quantitative analysis of genetic differentiation in human (and any other) populations. The key to the problem is to determine a start-point for detection of neutral genetic variability, which will help to establish alignment of adaptive and neutral forces operating in genetic differentiation. The purpose of this work is to adduce proofs in favour of mean Fst value for a sample of gene loci as of the start-point for measuring neutrality level of genetic differentiation. These proofs came from various demographic and onomastic characteristics of ethnic groups as well as from genetic chronology of ethnic history which is in good concordance with actual historical chronology of ethnic groups. Once the start-point for testing neutrality is determined, it becomes possible to reveal the selective pressure to which various human genes are undergone and to elucidate adaptive structure of mankind's genetic pool. It was shown that only 15 alleles from 49 belonging to 20 polymorphic loci can be considered selectively neutral.

Ethnicity↗

PubMed2004

Does receiving genetic counseling impact genetic counselor practice?

This study was an investigation of whether genetic counselors have received genetic counseling and if so, how they believe it affects their practice. One thousand genetic counselors were mailed surveys about the nature of genetic counseling services received, impact on their clinical practice, frequency and reasons for disclosing about their receipt of counseling to their clients, and demographics. Ninety-three of the 510 respondents reported receiving genetic counseling. Of these, almost three-fourths were practicing genetic counselors while receiving services. Reasons for services include prenatal concerns, family history of cancer, and history/risk of other genetic conditions. Frequently endorsed effects on practice include increased empathy and understanding of client decisions, feeling more connected with clients, greater emphasis on psychosocial support, and sympathy. Forty-six respondents disclosed to clients about their receipt of genetic counseling. Prevalent reasons include client asked, help clients feel they are not alone, demonstrate counselor understanding, decrease client anxiety, build rapport, and normalize client feelings. Practice and research recommendations are given.

Adult↗

PubMed2006

Genetic nurse counsellors can be an acceptable and cost-effective alternative to clinical geneticists for breast cancer risk genetic counselling. Evidence from two parallel randomised controlled equivalence trials.

This study compared genetic nurse counsellors with standard services for breast cancer genetic risk counselling services in two regional genetics centres, in Grampian region, North East Scotland and in Cardiff, Wales. Women referred for genetic counselling were randomised to an initial genetic counselling appointment with either a genetic nurse counsellor (intervention) or a clinical geneticist (current service, control). Participants completed postal questionnaires before, immediately after the counselling episode and 6 months later to assess anxiety, general health status, perceived risk and satisfaction. A parallel economic evaluation explored factors influencing cost-effectiveness. The two concurrent randomised controlled equivalence trials were conducted and analysed separately. In the Grampian trial, 289 patients (193 intervention, 96 control) and in the Wales trial 297 patients (197 intervention and 100 control) returned a baseline questionnaire and attended their appointment. Analysis suggested at least likely equivalence in anxiety (the primary outcome) between the two arms of the trials. The cost per counselling episode was 11.54 UK pounds less for nurse-based care in the Grampian trial and 12.50 UK pounds more for nurse-based care in Cardiff. The costs were sensitive to the grade of doctor (notionally) replaced and the extent of consultant supervision required by the nurse. In conclusion, care based on genetic nurse counsellors was not significantly different from conventional cancer genetic services in both trial locations.

Adolescent↗

PubMed1967

The genetic control of gamma-globulin heavy chains. Studies of the major heavy chain subgroup utilizing multiple genetic markers.

The genetic control of gammaG1-heavy chains was investigated by taking advantage of two recently described genetic antigens, Gm(z) and Gm(y), both produced by heteroimmunization of rabbits with myeloma proteins. These were studied in conjunction with known genetic markers, Gm(a) and Gm(f). The results indicated that among Caucasians there are two major allelic genes, Gm(za) and Gm(fy), coding for distinct varieties of gammaG1-heavy chains. Each of these contains a pair of genetic antigens which are located on different fragments of the chain and can be separated by enzymatic splitting with papain. The different areas of the heavy chains appear to be under the control of the same gene. In Mongoloid populations a grouping of three genetic antigens, Gm(f), (y), and (a), was found on isolated myeloma proteins and normal gamma-globulins indicating the presence of a Gm(fya) gene. The possible genetic events leading to the contrasting Caucasian and Mongoloid genes are discussed. In the gamma-globulin system the occurrence of multiple genetic antigens in different positions of the same heavy chains is the general rule. A better understanding of the relationships between the genes for the gammaG1-subgroup to those for the gammaG2- and gammaG3-subgroup has been obtained through the use of the multiple genetic markers. Strong evidence was obtained for intergenic crossover mechanisms to explain racial differences in the relationships of these genes as well as certain unusual gene complexes found through family studies. Further evidence was obtained for mapping the closely linked genes for the three subgroups in a specific order.

Black or African American↗

PubMed2005

Genetical genomics: combining genetics with gene expression analysis.

The biological mechanisms that link genetic variation and its phenotypic outcome stand as a central puzzle in biology. Geneticists have usually approached this problem by trying to identify genetic variants that underlie the trait in question. Ten years ago, microarray technology opened a second front by making it possible to compare expression levels for most active genes under a variety of genetic and environmental conditions. A typical study reveals up- or down-regulation of genes or pathways associated with a phenotype (case/control) or condition (treated/untreated). In the past few years, a number of groups have started to combine gene expression studies with genetic linkage analysis, leading to a new synergy between these approaches. In this strategy, expression levels are treated as quantitative phenotypes and genetic variants that influence gene expression are sought. Several studies have shown that mRNA levels for many genes are heritable, thus amenable to genetic analysis. Quantitative trait loci mapping efforts have led to the initial characterization of genetic regulation in 'cis' probably because of variants in the gene's own regulatory regions, as well as in 'trans', i.e. by loci elsewhere in the genome. The existence of some 'master regulators' that each affects expression levels of hundreds of genes is an important finding that will surely enrich our understanding of regulatory networks. Although this novel field is still developing, understanding the genetic basis of molecular phenotypes such as gene expression is expected to shed light on the intermediate processes that connect genotype to cellular and organismal traits and represents a critical step towards true systems biology.

Animals↗

PubMed2004

Relationship between the energetic cost of burrowing and genetic variability among populations of the pocket gopher, T. bottae: does physiological fitness correlate with genetic variability?

Many studies have reported relationships between genetic variability and fitness characters in invertebrates, but there is a paucity of such studies in mammals. Here, we use a statistically powerful paired sampling design to test whether the metabolic cost of burrowing, an important physiological trait in the pocket gopher, Thomomys bottae, correlates with genetic variability. Three pairs of pocket gopher populations were used, with each pair selected from a different subspecies and comprising one high genetic variability and one low genetic variability population. Genetic variability was measured using average allozyme heterozygosity and two measures of DNA fingerprint band sharing. In addition, the cost of burrowing for individuals from each population was determined from the oxygen consumption per gram of body mass per unit of work performed. Our results indicate that the cost of burrowing was significantly higher in populations with lower genetic variability (3-way ANCOVA, P=0.0150); mass-adjusted cost of burrowing in the low variability populations averaged 0.57+/-0.24 ml O2 g(-1) kgm(-1) and that in the high variability populations averaged 0.42+/-0.19 ml O2 g(-1) kgm(-1). The magnitude of the population differences in cost of burrowing was associated with the magnitude of difference in genetic variability. We conclude that population differences in genetic variability are reflected in physiological fitness differences for a trait that is essential to gopher survival.

Analysis of Variance↗

PubMed2005

Heritabilities, genetic correlations, and genetic change for female fertility and protein yield in Norwegian Dairy Cattle.

Data from 1,815,581 first insemination records from daughters of 2697 Norwegian Dairy Cattle (NRF) sires were analyzed. A multitrait model was used to estimate genetic parameters and genetic change for 56-d nonreturn rate in virgin heifers (NR56D0), for 56-d nonreturn rate in first lactation cows (NR56D1L), for interval from calving to first insemination (CFI1L), and for protein yield (PY(305)1L). The heritabilities for NR56D0, NR56D1L, CFI1L, and PY(305)1L were 1.08, 0.99, 3.01, and 20.80%, respectively. Genetic correlation between heifer and cow fertility was high and favorable between NR56D0 and NR56D1L (0.54) and moderate and unfavorable between NR56D0 and CFI1L (0.24). The genetic correlations between NR56D1L and CFI1L and between NR56D0 and PY(305)1L were 0.08 and 0.04, respectively. A small, unfavorable genetic correlation between NR56D1L and PY(305)1L (-0.18) was found, while the genetic correlation between PY(305)1L and CFI1L was strongly unfavorable (0.47). Since 1972, NRF sires have been selected for NR56D0 using breeding values estimated from large progeny groups and with considerable weight in the total merit index. A linear regression analysis of sire PTA on year of first insemination of daughters showed an annual genetic change of 0.14% units for NR56D0. Selection was able to stabilize the genetic change of NR56D1L (0.03%/yr) but an undesirable change for CFI1L (0.11 d/yr) was found. The change of sire PTA for PY(305)1L was 0.63 kg/yr.

Analysis of Variance↗

PubMed1998

Genetic control of blood infection levels in human malaria: evidence for a complex genetic model.

There is now accumulating evidence for the involvement of genetic factors in the control of immune response against malaria. These arguments come from numerous animal models, from population studies showing associations of red blood cell genetic defects as well as HLA antigens with severe malaria, and from familial studies including a recent segregation analysis, which led to detection of a major gene effect predisposing to high infection levels. The heterogeneity and complexity of this genetic control is one of the main findings of these previous studies, and probably a major cause of the difficulty in developing an effective malaria vaccine. A segregation analysis of blood infection levels is performed here in 44 pedigrees living in the tropical rain forest of southern Cameroon and exposed to high vectorial transmission intensity. The results confirm the existence of complex genetic factors controlling blood infection levels in human malaria but are not consistent with the parent-offspring transmission of a single Mendelian gene. This study also shows the dramatic effect of age on infection levels and its interaction with a putative major gene suggesting that genetic related differences are much more important in children than in adults. Further genetic studies focused on children may help to identify the nature of the genetic factors involved in the expression of human malaria, by means of linkage analyses using both familial information and genetic markers.

Adolescent↗

PubMed2026

Genetic evidence prioritizes circulating proteins for heart failure beyond shared BMI-related genetic liability.

BACKGROUND: Heart failure (HF) and body mass index (BMI) share substantial genetic architecture, which may lead genetically informed target discovery to preferentially identify adiposity-related pathways. We sought to identify circulating proteins associated with HF beyond this shared genetic component. METHODS: We applied GWAS-by-subtraction to overall HF, nonischemic HF, and nonischemic HF with reduced or preserved ejection fraction to derive BMI-related and BMI-subtracted HF components. We then performed proteome-wide cis-pQTL Mendelian randomization and colocalization using four independent proteomic cohorts, followed by tissue-specific eQTL colocalization, cardiac transcriptomic annotation, and druggability assessment. RESULTS: Compared with the original HF phenotypes, the BMI-subtracted components showed attenuated genetic correlations with BMI (0.045-0.147) while retaining 28 independent loci for overall HF and nine for nonischemic HF. Across 19,930 protein-HF tests, 11 associations involving nine proteins were prioritized by the Mendelian randomization and colocalization analyses. For example, a 1-SD increase in genetically predicted CELSR2 abundance was associated with lower overall HF risk (odds ratio, 0.96 [95% CI, 0.94-0.98]; P=8.6×10-7), whereas a 1-SD increase in genetically predicted CSF3 abundance was associated with higher nonischemic HF risk (odds ratio, 1.32 [95% CI, 1.18-1.48]; P=2.0×10-6). CELSR2 and TMEM106B colocalized with cis-eQTLs in failing left ventricular myocardium, and DAG1 showed cardiomyocyte enrichment with concordant downregulation in failing hearts. CONCLUSIONS: We identified nine circulating proteins associated with HF beyond the genetic component shared with BMI. These findings extend the range of genetically supported pathways implicated in HF and nominate candidate proteins for further mechanistic and therapeutic investigation.

Genetics↗

PubMed1990

Teaching genetics to medical students. Report of a Working Party of the Clinical Genetics Committee of the Royal College of Physicians.

Rapid developments in molecular biology coupled with increased patient awareness and expectations emphasize the importance of ensuring that medical students are familiar with the principles of human genetics and their applications in clinical and preventive medicine. The present survey by the Royal College of Physicians of British medical schools revealed very variable teaching of genetics with a mean of 20 hours pre-clinical (range 2-66 hours) and 5.5 hours timetabled clinical teaching. Teaching was given by many different departments and was generally of unknown quality or clinical relevance. In contrast, a questionnaire survey of pre-clinical and clinical teachers in the main subjects and specialties demonstrated strong and consistent support for a genetic curriculum and the development of basic genetic skills by students by the end of the medical course. In view of this response, recommendations are made to institute a genetic core curriculum with a framework of timetabled clinical genetic teaching. It is also recommended that a Genetic Education Task Group be established to co-ordinate implementation and to ensure the clinical relevance of genetic teaching.

Attitude↗

PubMed1995

Genetics in cancer prediction, screening, and counseling: Part II, The nurse's role in genetic counseling.

PURPOSE/OBJECTIVES: To describe an expanded role for oncology nurses in genetic counseling for cancer. DATA SOURCES: Published professional articles, computerized data bases, lay publications. DATA SYNTHESIS: A description of the availability of genetic counseling, of motivation for undergoing genetic counseling, and of the basic components of genetic counseling for cancer. CONCLUSIONS: The need for genetic counseling will increase as more families with inherited cancer are identified, more cancer genes are isolated, and genetic analysis becomes more available. IMPLICATIONS FOR NURSING PRACTICE: Advances in genetic technology provide nurses with the opportunity for an expanded role in genetic counseling for cancer. Oncology nurses also can act as case finders of families with inherited cancers and conduct research in this area.

Genetic Counseling↗

PubMed1996

Genetic variation in the population of Ibiza (Spain): genetic structure, geography, and language.

A sample of 203 individuals from Ibiza (Balearic Islands, Spain) were tested for blood group and serum protein genetic variation and compared with other circum-Mediterranean populations. Allele frequencies were calculated for the following blood group and serum systems: ABO, Rh, MNSs, P, Lewis, Duffy, Kell, ORM, GC, TF, PI, and HP. The allele frequencies from Ibiza were compared with those from other Balearic Islands (Majorca and Minorca) and with related European and North African groups using an assortment of analytical methods (genetic distances, R matrix analysis, and Mantel tests). R matrix analysis revealed that Ibiza is genetically different from the other Balearic populations and, because of gene flow from Spain, clusters with European groups. The level of genetic microdifferentiation of the Mediterranean populations, measured by RST (average of the R matrix diagonal elements, rii), is 0.028. An examination of the relationship between genetic, geographic, and linguistic distances by Mantel tests revealed that genetic distances are significantly correlated with linguistic distances, whereas the genetic distances are not significantly correlated with geographic distances. The plot of mean per locus heterozygosity versus the genetic distance from the centroid of distribution revealed that all three Balearic Islands have experienced considerable gene flow but that Ibiza has been most affected by the action of stochastic processes.

Blood Group Antigens↗

PubMed2006

Ethical and clinical practice considerations for genetic counselors related to direct-to-consumer marketing of genetic tests.

Several companies utilize direct-to-consumer (DTC) advertising for genetic tests and some, but not all, bypass clinician involvement by offering DTC purchase of the tests. This article examines how DTC marketing strategies may affect genetic counselors, using available cardiovascular disease susceptibility tests as an illustration. The interpretation of these tests is complex and includes consideration of clinical validity and utility, and the further complications of gene-environment interactions and pleiotropy. Although it is unclear to what extent genetic counselors will encounter clients who have been exposed to DTC marketing strategies, these strategies may influence genetic counseling interactions if they produce directed interest in specific tests and unrealistic expectations for the tests' capacity to predict disease. Often, a client's concern about risk for cardiovascular diseases is best addressed by established clinical tests and a family history assessment. Ethical dilemmas may arise for genetic counselors who consider whether to accept clients who request test interpretation or to order DTC-advertised tests that require a clinician's authorization. Genetic counselors' obligations to care for clients extend to interpreting DTC tests, although this obligation may be fulfilled by referral or consultation with specialists. Genetic counselors do not have an obligation to order DTC-advertised tests that have minimal clinical validity and utility at a client's request. This can be a justified restriction on autonomy based on consideration of risks to the client, the costs, and the implications for society.

Cardiovascular Diseases↗

PubMed2006

Genetic distance sampling: a novel sampling method for obtaining core collections using genetic distances with an application to cultivated lettuce.

This paper introduces a novel sampling method for obtaining core collections, entitled genetic distance sampling. The method incorporates information about distances between individual accessions into a random sampling procedure. A basic feature of the method is that automatically larger samples are obtained if accessions are further apart and smaller samples if accessions are closer together. Genetic distance sampling can be used in conjunction with predefined stratifications of the accessions. Sample sizes are determined automatically; they depend on the distances between accessions within strata. The method is applied to the collection of cultivated lettuce of the Centre for Genetic Resources, the Netherlands. In this paper, genetic distances between accessions are obtained using AFLP marker data. However, genetic distance sampling can be applied using any measure of genetic distance between accessions. Some properties of genetic distance sampling are discussed.

Agriculture↗

PubMed2006

Genetics of symbiosis in Lotus japonicus: recombinant inbred lines, comparative genetic maps, and map position of 35 symbiotic loci.

Development of molecular tools for the analysis of the plant genetic contribution to rhizobial and mycorrhizal symbiosis has provided major advances in our understanding of plant-microbe interactions, and several key symbiotic genes have been identified and characterized. In order to increase the efficiency of genetic analysis in the model legume Lotus japonicus, we present here a selection of improved genetic tools. The two genetic linkage maps previously developed from an interspecific cross between L. japonicus Gifu and L. filicaulis, and an intraspecific cross between the two ecotypes L. japonicus Gifu and L. japonicus MG-20, were aligned through a set of anchor markers. Regions of linkage groups, where genetic resolution is obtained preferentially using one or the other parental combination, are highlighted. Additional genetic resolution and stabilized mapping populations were obtained in recombinant inbred lines derived by a single seed descent from the two populations. For faster mapping of new loci, a selection of reliable markers spread over the chromosome arms provides a common framework for more efficient identification of new alleles and new symbiotic loci among uncharacterized mutant lines. Combining resources from the Lotus community, map positions of a large collection of symbiotic loci are provided together with alleles and closely linked molecular markers. Altogether, this establishes a common genetic resource for Lotus spp. A web-based version will enable this resource to be curated and updated regularly.

Alleles↗