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PubMed1992

Sheep blood polymorphism and genetic divergence between French Rambouillet and Spanish Merino: role of genetic drift.

Rambouillet sheep originating from Spanish Merino have been maintained in France as a small and closed flock since their importation. After 190 years of independent evolution, the flock has markedly differentiated from its Spanish parental population. The observed differences between them were characterized by the fixation in Rambouillet of the Mb and F30 alleles, which occurred in Spanish Merino with frequencies of 0.90 and 0.80 respectively (at two distinct blood group loci M and F30) and by the absence in Rambouillet of other alleles or phenogroups (at the Tf and the A, B, C blood group loci) which were observed in Spanish Merino with frequencies ranging from 0.10 to 0.28. On the basis of their phenotypic distributions at 11 blood polymorphic loci, the two populations differed significantly from each other (total chi 2 values = 352.62, 23 df, P less than 0.001). By comparing the observed magnitude of gene frequency differences between Rambouillet and Spanish Merino with the estimate of inbreeding coefficient for Rambouillet obtained from pedigrees, it appeared that the observed genetic differences could be attributed to the evolutionary change due to random drift in the small and closed flock of Rambouillet.

Animals↗
PubMed2006

Population genetic structuring of the king weakfish, Macrodon ancylodon (Sciaenidae), in Atlantic coastal waters of South America: deep genetic divergence without morphological change.

Phylogeographic patterns in Macrodon ancylodon sampled from 12 locations across all its range were investigated using mitochondrial DNA cytochrome b sequences, and analysed together with patterns of morphometric differentiation. Populations of the North Brazil and the Brazil currents, with warmer waters, form a clade (tropical clade) separated by 23 fixed mutations from the populations that inhabit regions of colder waters influenced by the Brazil and Malvinas currents (subtropical clade). No gene flow exists between the tropical and subtropical clades, and most likely also between the two groups of the tropical clade. Distribution of these clades and groups is correlated with flow of currents and their temperatures, and is facilitated by larval retention and low adult migration. Despite differentiation at the molecular level, fishes analysed from all these current-influenced regions are morphometrically homogeneous. Throughout its range M. ancylodon inhabits the same, or very similar niche; thus, stabilizing selection probably promotes the retention of highly conserved morphology despite deep genetic divergence at the mitochondrial DNA cytochrome b.

Animals↗
PubMed1996

Prenatal genetic services for Down's syndrome: access and provision in 1990-1991. Steering Committee of the National Confidential Enquiry into Counselling for Genetic Disorders.

OBJECTIVE: To examine access to and provision of prenatal genetic services relating to Down's syndrome. DESIGN: Retrospective review of obstetric casenotes. SAMPLE: Pregnancies involving Down's syndrome in England and Wales in 1990-1991 in women aged 38 or over. Information was obtained in 430 cases from a questionnaire completed by the obstetric team who were asked to provide details based only on documentation in the antenatal casenotes. The outcome of pregnancy was a termination in 268 (62%) cases, a liveborn child with Down's syndrome in 144 (34%), a stillbirth in 9 (2%), a miscarriage in 8(2%) and in one case was not known. RESULTS: Overall, prenatal diagnosis was not offered in 7% pregnancies (95% CI: 4.4-9.2%) with late booking given as the main reason. Of women offered prenatal diagnosis, 76% accepted (95% CI: 72.3-80.6%). Counselling was documented before prenatal diagnosis in 89% of cases (95% CI: 86.0-92.3%) and after the procedure, to discuss the results, in 73% (95% CI: 67.5-77.7%). In 10% of pregnancies terminated for Down's syndrome, fetal products were not sent to the laboratory. There was no report of a normal fetus having been terminated as a consequences of incorrect prenatal diagnosis. However, in 10% (95% CI: 5.9 to 14.0%) of cases examined in the laboratory the diagnosis of Down's syndrome could not be confirmed. Details of prenatal diagnosis were not provided in five cases where a child with Down's syndrome was born. Of the remaining 139 livebirths, prenatal diagnosis was not offered in 27 (19%) cases, offered and declined in 92 (66%) and accepted in 20 (14%). In two cases a normal fetal karyotype was reported following prenatal diagnosis. CONCLUSIONS: The study has demonstrated that in 1990-1991: 1. There were certain shortcomings in the documentation of antenatal care; 2. Late booking was the main factor precluding the offer of prenatal diagnosis to women aged 38 or over, and 3. The rate of confirmation of Down's syndrome in terminated fetuses was incomplete.

Abortion, Induced↗
PubMed1997

Epilepsy genes and the genetics of epilepsy syndromes: the promise of new therapies based on genetic knowledge.

Treatment strategies based on the molecular biology of the epilepsies may soon become a reality. Critical steps in this process are identifying molecular genetic defects in specific epilepsies, understanding of the neurobiologic consequences of those defects, and developing methods to correct the molecular defects or their downstream consequences. Identification of molecular defects is easier in single-gene epilepsies than in those with complex inheritance, although the latter are more common. A number of epilepsies have been mapped and, in two cases, specific genes have been identified. Unverricht-Lundborg disease is caused by defects in the cystatin B gene, with absence of the gene product. Autosomal dominant nocturnal frontal lobe epilepsy in some families is caused by mutations in the alpha4-subunit of the nicotinic acetylcholine receptor gene. In vitro studies suggest that the mutations lead to impaired function of the acetylcholine receptor, raising the possibility of cholinergic therapy for this condition. Advances in the molecular biology of the epilepsies are likely to change our understanding radically and to allow opportunities to develop innovative new treatments for epilepsy.

Animals↗
PubMed1974

Genetic analyses of the polarity alleles in recombinants from mitochondrial genetic crosses.

A number of minority recombinant and parental types from a heterosexual cross were analyzed for the omega allele they carry. It was found that recombinant progeny can be omega(-), that minority parental types among the progeny can be omega(+) rather than omega(-), and, finally, that certain of the results suggest that the omega locus may not be at the proximal end of the mitochondrial genetic map (Bolotin et al., 1971; Grivell et al., 1973) but rather may lie between the [cap1-r/cap-s] and [ery1-r/ery-s] loci.

Alleles↗
PubMed1981

Genetics society of Canada award of excellence lecture. The genetics of common familial disorders--major genes or multifactorial?

The common familial disorders were, until recently, neglected by geneticists because their familial distributions did not neatly fit the Mendelian mold, and no specific genes could be identified. The multifactorial-threshold model made the familial characteristics of these disorders more intelligible. Although it originally postulated a polygenic genetic component the model can also accommodate one or more major genes with low penetrance. The resulting upsurge of interest has led to (1) the development of increasingly sophisticated mathematical models from which to calculate recurrence risks for specific family situations and (2) the identification of specific predisposing genes in a number of such disorders. One of the corollaries of the model is that any pharmacological agent at therapeutic doses is likely to be teratogenic to at least some embryos, so that regulation should be in terms of "acceptably low" levels of teratogenicity rather than "safety".

Abnormalities, Drug-Induced↗
PubMed2002

Genetic "code": representations and dynamical models of genetic components and networks.

Dynamical modeling of biological systems is becoming increasingly widespread as people attempt to grasp biological phenomena in their full complexity and make sense of an accelerating stream of experimental data. We review a number of recent modeling studies that focus on systems specifically involving gene expression and regulation. These systems include bacterial metabolic operons and phase-variable piliation, bacteriophages T7 and lambda, and interacting networks of eukaryotic developmental genes. A wide range of conceptual and mathematical representations of genetic components and phenomena appears in these works. We discuss these representations in depth and give an overview of the tools currently available for creating and exploring dynamical models. We argue that for modeling to realize its full potential as a mainstream biological research technique the tools must become more general and flexible, and formal, standardized representations of biological knowledge and data must be developed.

Animals↗
PubMed1996

Genetic and biochemical factors associated with variation in blood pressure in a genetic isolate.

We previously found an association between blood pressure and genetic variation of angiotensinogen in Canadian Hutterites. We hypothesized that variation in other candidate genes would also be associated with variation in blood pressure. We included genotypes of 12 candidate genes, along with clinical features and biochemical variables as covariates in an association analysis. We found that sex and body mass were significantly associated with variation in both systolic and diastolic blood pressures. We found that genotypes of APOB codon 4154 and AGT codon 174 were significantly associated with variation in systolic blood pressure. We found that genotypes of APOB codon 4154, AGT codon 174, and F7 codon 353 were significantly associated with variation in diastolic blood pressure. We found a significant association between age and variation in systolic but not diastolic blood pressure. We found a significant association between plasma apo B concentration and variation in diastolic but not systolic blood pressure. The association of genomic variation with resting blood pressure is consistent with the existence of important structural elements within or proximal to some genes in lipoprotein metabolism, the renin-angiotensin system, and the coagulation cascade. The association between plasma apo B concentration and diastolic blood pressure suggests that these traits may share some determinants.

Angiotensinogen↗
PubMedDate not supplied

Genetic engineering in agriculture and corporate engineering in public debate: risk, public relations, and public debate over genetically modified crops.

Corporations have long influenced environmental and occupational health in agriculture, doing a great deal of damage, making substantial profits, and shaping public debate to make it appear that environmental misfortunes are accidents of an otherwise well-functioning system, rather than systemic. The debate over the genetically modified (GM) crops is an example. The largest producer of commercial GM seeds, Monsanto, exemplifies the industry's strategies: the invocation of poor people as beneficiaries, characterization of opposition as technophobic or anti-progress, and portrayal of their products as environmentally beneficial in the absence of or despite the evidence. This strategy is endemic to contemporary market capitalism, with its incentives to companies to externalize health and environmental costs to increase profits.

Agriculture↗
PubMed1993

Genetic heterogeneity of autosomal dominant cerebellar ataxia type 1: clinical and genetic analysis of 10 French families.

We performed linkage analysis between the gene responsible for spinal cerebellar ataxia 1 (SCA1) and the highly polymorphic chromosome 6 locus, D6S89, in 10 French families with autosomal dominant cerebellar ataxia (ADCA) type 1. These families were clinically indistinguishable except for one family with loss of hearing and vision. Very close linkage was observed in four families, with no evidence of recombination between SCA1 and D6S89. Linkage with D6S89 was excluded in the six others, thus demonstrating genetic heterogeneity for ADCA type 1. The D6S89 marker, which is very closely linked to the disease locus, can be used to identify SCA1 families and will lead to predictive testing.

Adult↗
PubMed2006

[Genetic screening of multiple endocrine neoplasia type 2: experience of the USP Endocrine Genetics Unit].

Multiple endocrine neoplasia type 2 (MEN-2) is an inherited tumor syndrome that includes medullary thyroid carcinoma (MTC), primary hyperparathyroidism, pheochromocytoma and other non-endocrine diseases. Since the first RET missense mutations in association with MEN-2 were identified, RET mutation analysis had a great impact in the clinical management of MEN-2, such as in early diagnosis and treatment of MTC. Presently, early total thyroidectomy provides real cure of MTC for cases in which molecular diagnosis has been performed at early ages. After RET mutation identification, family members should be screened for this mutation by using methods as DGGE, SSCP, restriction enzyme, genetic sequencing or mini-sequencing. In this paper, we briefly review our experience with the direct RET gene sequencing and DGGE approaches. In 50 typical MEN-2 patients analyzed using both methods, we found no false results suggesting that DGGE is a reliable screening method for RET proto-oncogene mutation analysis.

Algorithms↗
PubMed1994

Optimal contemporary group structure to maximize genetic progress through genetic evaluation of swine.

Accuracies of sire EPD were calculated for a typical growth trait and a typical maternal trait for alternative contemporary group structures. For a given family size (number of progeny tested for a sire in a contemporary group), accuracy increased as the number of sires increased and as the number of contemporary groups increased. An exponential equation was found to best predict accuracy from the number of sires and groups. Partial derivatives can be used to determine the optimal number of sires and groups for a given economic situation (fixed number of animals tested per group). It is recommended that progeny of at least two sires be represented in each contemporary group, but having more than five sires does not effectively increase accuracy further. Accuracy increases with a larger herd size, as more sires and more groups of pigs are tested. When the number of litters that can be tested is at its limit, accuracy is maximized with a small number of sires, and progeny divided among several contemporary groups. However, accuracy is only part of the herd's genetic improvement. Selection decisions must be made to avoid inbreeding, which can be a problem, particularly in small herds.

Animals↗
PubMed1991

Genetics of growth and reproduction in the turkey. 11. Evidence of nonadditive genetic variation.

A commercial sire line (C) and an experimental population selected solely for increased 16-wk BW (F) were reciprocally crossed to produce crossbred F1 and F2 progeny. The F1 and F2 crosses were used to evaluate the presence of nonadditive genetic variance for growth and reproductive traits. The crosses demonstrated improved growth performance as indicated by heterosis for 16- and 20-wk BW. The difference in BW was, however, reversed at maturity as indicated by negative heterosis for BW at maturity. The F1 and F2 crosses also exhibited heterosis for walking ability. Heterosis for reproductive traits was greater than for growth. The F1 crosses produced approximately 20 eggs more in a 180-day production season than the parental populations. This difference was halved in F2 generation hens. Improved egg production was achieved both through an increase in the rate of egg production and through a reduction in broodiness. The present experiment indicates that there is potential for significant heterosis for growth and reproduction in some crosses in the domestic turkey. The results also indicate that heterosis can be considerable, even in crosses of lines which do not differ greatly in BW or reproductive performance.

Animals↗
PubMed2000

Autosomal-dominant giant platelet syndromes: a hint of the same genetic defect as in Fechtner syndrome owing to a similar genetic linkage to chromosome 22q11-13.

Families with 3 different syndromes characterized by autosomal dominant inheritance of low platelet count and giant platelets were studied. Fechtner syndrome is an autosomal-dominant variant of Alport syndrome manifested by nephritis, sensorineural hearing loss, and cataract formation in addition to macrothrombocytopenia and polymorphonuclear inclusion bodies. Sebastian platelet syndrome is an autosomal-dominant macrothrombocytopenia combined with neutrophil inclusions that differ from those found in May-Hegglin syndrome or Chediak-Higashi syndrome or the Dohle bodies described in patients with sepsis. These inclusions are, however, similar to those described in Fechtner syndrome. Other features of Alport syndrome, though, including deafness, cataracts, and nephritis, are absent in Sebastian platelet syndrome. Epstein syndrome is characterized by macrothrombocytopenia without neutrophil inclusions, in addition to the classical Alport manifestations-deafness, cataracts, and nephritis-and it is also inherited in an autosomal-dominant mode. We mapped the disease-causing gene to the long arm of chromosome 22 in an Italian family with Fechtner syndrome, 2 German families with the Sebastian platelet syndrome, and an American family with the Epstein syndrome. Four markers on chromosome 22q yielded an LOD score greater than 2.76. A maximal 2-point LOD score of 3.41 was obtained with the marker D22S683 at a recombination fraction of 0.00. Recombination analysis placed the disease-causing gene in a 3.37-Mb interval between the markers D22S284 and D22S693. The disease-causing gene interval in these 3 syndromes is similar to the interval described recently in an Israeli family with a slightly different Fechtner syndrome than the one described here. Recombination analysis of these 3 syndromes refines the interval containing the disease-causing gene from 5.5 Mb to 3.37 Mb. The clinical likeness and the similar interval containing the disease-causing gene suggest that the 3 different syndromes may arise from a similar genetic defect.

Bernard-Soulier Syndrome↗
PubMedDate not supplied

[Human genetics studies in areas of high natural radiation. VII. Genetic load].

Two methods to estimate the inbreeding load (Morton, Crow and Muller17 1956; Freire-Maia and Freire-Maia6 1965) are reviewed. Both are employed in the analysis of our data. Besides the total population, a sample constituted of individuals with no alien ancestral is also analysed. No clean effect of natural radioactivity, as measured by genetic load models, has been found (this is especially valid for abortions, pre-natal mortality, anomalies, and abnormalities in general). The results on stillbirths and post-natal and total mortalities are discussed, and it is concluded that most probably the differences found are due to uncontrolled concomitant variables (if not to chance alone). Further analysis are under way.

Brazil↗
PubMed2004

[The relationship between genetic polymorphism of metabolizing enzymes and the genetic susceptibility to lung cancer].

OBJECTIVE: To investigate the relationship between the gene polymorphism of metabolizing enzymes and the genetic susceptibility to lung cancer as well as to study the synergistic effects between smoking and the genes. METHODS: A case-control study (case = 217, control = 200) was carried out to compare the frequent distribution of CYP1A1, 2E1, 2D6 and GSTM1 genotypes between the lung cancer group and the control group with a polymerase chain reaction-restriction fragment polymorphism (PCR-RFLP) method and to analyze the relationship between these genes and smoking. RESULTS: GSTM1-null genotype frequency was 58.5% in the lung cancer group and 47.5% in the control group with significant difference (P = 0.02). The frequent distribution of CYP1A1, 2E1, 2D6 genotypes was not significantly different in the two groups (P > 0.05). Synergistic effects were found between smoking and GSTM1 but not between smoking and CYP1A1, 2E1, 2D6. CONCLUSION: Smoking and GSTM1-null genotype seemed to be the risk factors of lung cancer. Those who carrying GSTM1-null genotype and smoking cigarettes were prone to suffer from lung cancer to become the high-risk population of the disease.

Cytochrome P-450 CYP1A1↗
PubMedDate not supplied

Quantification of the 35S promoter in DNA extracts from genetically modified organisms using real-time polymerase chain reaction and specificity assessment on various genetically modified organisms, part I: operating procedure.

A highly sensitive quantitative real-time assay targeted on the 35S promoter of a commercial genetically modified organism (GMO) was characterized (sF/sR primers) and developed for an ABI Prism 7700 Sequence Detection System and TaqMan chemistry. The specificity assessment and performance criteria of sF/sR assay were compared to other P35S-targeted published assays. sF/sR primers amplified a 79 base pair DNA sequence located in a part of P35S that is highly conserved among many caulimovirus strains, i.e., this consensus part of CaMV P35S is likely to be present in many GM events. According to the experimental conditions, the absolute limit of detection for Bt176 corn was estimated between 0.2 and 2 copies of equivalent genome (CEG). The limit of quantification was reached below 0.1% Bt176 content. A Cauliflower Mosaic Virus control (CaMV) qualitative assay targeted on the ORF III of the viral genome was also used as a control (primers 3F/3R) to assess the presence of CaMV in plant-derived products. The specificity of this test was assessed on various CaMV strains, including the Figwort Mosaic Virus (FMV) and solanaceous CaMV strains. Considering the performance of sF/sR quantification test, the highly conserved sequence, and the small size of the amplicon, this assay was tested in a collaborative study in order to be proposed as an international standard.

DNA Primers↗
PubMedDate not supplied

[Molecular-genetic analysis of wheat (T. aestivum L.) genome with introgression of Ae. cylindrica Host genetic elements].

Wheat-aegilops hybrid plants Triticum aestivum L. (2n = 42) x Aegilops cylindrica Host (2n = 28) were investigated with using microsatellite markers. In two BC1F9 lines some genome modifications connected with losing DNA fragments of initial variety or appearing of Aegilops genome elements were detected. In some investigated hybrids new amplicons lacking in parental plants were found. Substitution of wheat chromosomes for aegilops chromosomes was not revealed. Analysis of microsatellite loci in BC2F5 plants showed stable introgression of aegilops genetic elements into wheat; elimination of some transferred aegilops DNA fragments in the course of backcrossing; decreasing size of introgressive elements after backcrossing. Introgressive lines were classified according to genome changes.

Alleles↗