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PubMedDate not supplied

Evidence for a genetic variation in the mitochondrial genome affecting traits in White Leghorn chickens.

A mitochondrial Mspl RFLP which was coselected with Marek's disease (MD) resistance in White Leghorn chickens was mapped to the NADH subunit IV. The RFLP was due to a transition, resulting in the change of the low-usage threonine triplet ACT (Mspl- allele) to the high usage triplet ACC (Mspl+ allele). Trait association studies within an unselected strain revealed that the Mspl- allele whose frequency was reduced in MD resistant strains was associated with high body weight and high egg specific gravity (a measure of eggshell thickness). Analysis at three different time points indicated a significant interaction between the mitochondrial genotype and the growth hormone genotype in early but not in late adulthood. The analysis indicates that mitochondrial variants may contribute to phenotypic variation in chickens and that such contributions may be dependent on the genetic background.

Animals↗
PubMedDate not supplied

[Comparative analysis of genetic variation in two groups of Crimean pine trees with different levels of tolerance to industrial pollutants in the environs of the city of Mariupol].

The comparative analysis of genetic variability of two groups of young Pinus pallasiana D. Don. trees with different degree of tolerance to industrial pollution, defined in plantations of Mariupol and its environs, has been performed on the basis of polymorphism investigations in 20 isoenzyme loci controlling 9 enzyme systems. In these groups of plants with high and low quantity of needles on the growing sprouts differences in the levels of genetic variability, as to average criteria, have not been found.

Alleles↗
PubMed2004

Biogeographic patterns and current distribution of molecular-genetic variation among populations of speckled dace, Rhinichthys osculus (Girard).

We examined genetic diversity within- and among-populations of speckled dace (Rhinichthys osculus) in five major drainage systems in the state of Oregon in western North America. Analysis of sequence variation in a 670-bp segment of the mitochondrial cytochrome b gene revealed deep divergence among basins and high genetic diversity within basins. Application of a molecular clock indicated that the divergence time among basins reflects vicariant events during the late Miocene to early Pliocene. The high levels of genetic diversity observed within basins is likely due to large historic population sizes, in particular, within the Klamath Basin. Two highly divergent mtDNA lineages were found to co-occur in populations in the Klamath Basin. This result may be indicative of a complex history of isolation and reconnection in this basin and/or multiple colonization events. Based on the observed level of mtDNA divergence these lineages may represent two reproductively isolated sympatric taxa. We recommend that major basins be regarded as distinct ESUs based on high levels of subdivision, deep divergences, and reciprocal monophyly among basins.

Animals↗
PubMed2005

Genetic variation and migration in the Mexican free-tailed bat (Tadarida brasiliensis mexicana).

Incomplete lineage sorting can genetically link populations long after they have diverged, and will exert a more powerful influence on larger populations. The effects of this stochastic process can easily be confounded with those of gene flow, potentially leading to inaccurate estimates of dispersal capabilities or erroneous designation of evolutionarily significant units (ESUs). We have used phylogenetic, population genetic, and coalescent methods to examine genetic structuring in large populations of a widely dispersing bat species and to test hypotheses concerning the influences of coalescent stochasticity vs. gene flow. The Mexican free-tailed bat, Tadarida brasiliensis mexicana, exhibits variation in both migratory tendency and route over its range. Observations of the species' migratory behaviour have led to the description of behaviourally and geographically defined migratory groups, with the prediction that these groups compose structured gene pools. Here, we used mtDNA sequence analyses coupled with existing information from allozyme, banding, and natural history studies to evaluate hypotheses regarding the relationship between migration and genetic structure. Analyses of molecular variance revealed no significant genetic structuring of behaviourally distinct migratory groups. Demographic analyses were consistent with population growth, although the timing of population expansion events differs between migratory and nonmigratory populations. Hypotheses concerning the role of gene flow vs. incomplete lineage sorting on these data are explored using coalescent simulations. Our study demonstrates the importance of accounting for coalescent stochasticity in formulating phylogeographical hypotheses, and indicates that analyses that do not take such processes into account can lead to false conclusions regarding a species' phylogeographical history.

Analysis of Variance↗
PubMed2000

Genetic variations among Mycoplasma bovis strains isolated from Danish cattle.

The genetic heterogeneity of Mycoplasma bovis strains isolated in Denmark over a 17-year period was investigated. Forty-two field strains isolated from different geographic locations and specimens, including strains from 21 herds involved in two outbreaks of M. bovis-induced mastitis, and the type strain of M. bovis (PG45(T)) were assayed for variations in the BglII and MfeI restriction sites in the chromosomal DNA by using the amplified fragment length polymorphism (AFLP) fingerprinting technique. The obtained genomic fingerprints consisted of 62-68 AFLP fragments in the size range of 50-500 bp. Among the analyzed strains, 18 different AFLP profiles were detected. The similarity between individual fingerprints, calculated by Dice similarity coefficient, ranged from 0.9 to 1.0. Twenty-five strains, including 23 which were isolated during two outbreaks of M. bovis-induced mastitis which occurred 2 years apart, showed indistinguishable AFLP patterns. More genetic diversity was observed among the recent strains. The similarity of the genotypes of the field strains to that of the M. bovis type strain (PG45(T)) was 97.7%. The results of this study have demonstrated a remarkable genomic homogeneity of Danish strains of M. bovis that were probably epidemiologically related and which have remained stable for a considerable length of time. Furthermore, this study has demonstrated that AFLP can be used for genomic fingerprinting and discrimination of M. bovis strains.

Animals↗
PubMed2000

Genetic variation in LMNA modulates plasma leptin and indices of obesity in aboriginal Canadians.

We previously showed that a rare mutation in LMNA, which encodes lamins A and C, underlies autosomal dominant Dunnigan-type familial partial lipodystrophy (FPLD). Because FPLD is an extreme example of genetically disturbed adipocyte differentiation, it is possible that common variation in LMNA is associated with obesity-related phenotypes. We therefore analyzed the relationships between the common LMNA 1908T/C single nucleotide polymorphism (SNP) and plasma leptin and anthropometric indices in 306 nondiabetic Canadian Oji-Cree. We found that subjects with the LMNA 1908T/1908T genotype had significantly higher plasma leptin than the subjects with either the 1908C/1908T or 1908C/1908C genotypes, after adjustment for age and sex. Physical indices of obesity, such as body mass index, percent body fat, and ratio of waist-to-hip circumference, were also higher among Oji-Cree subjects with the LMNA 1908T/1908T genotype than the subjects with either the 1908C/1908T or 1908C/1908C genotypes. The results suggest that common genetic variation in LMNA may be an important determinant of plasma leptin and obesity-related quantitative traits.

Adult↗
PubMed2002

Genetic variation in the cholesterol 24-hydroxylase (CYP46) gene and the risk of Alzheimer's disease.

Alzheimer's disease (AD) is a complex, multifactorial disorder, with many genetic and environmental factors implicated in disease onset and pathology. Increasing evidence points to a link between brain cholesterol turnover and AD. The CYP46 gene encodes for the enzyme, cholesterol 24-hydroxylase, which plays a key role in brain cholesterol turnover. A polymorphism in Intron 2 (T-->C) in the CYP46 gene has recently been reported to be associated with the risk of AD. In the present study, we examined the association of this CYP46 polymorphism with sporadic late-onset AD (LOAD) in American White (434 cases, 401 controls) and African American (54 cases, 61 controls) cohorts. No significant association was observed between the CYP46 polymorphism and LOAD. When the data were stratified by the apolipoprotein E*4 carrier status, no significant difference was observed between cases and controls for the CYP46 single nucleotide polymorphism. In addition, no significant difference in genotype or allele frequency was observed when stratified by the presence or absence of the alpha1-antichymotrypsin*A allele. Our data indicate that the Intron 2 polymorphism of CYP46 does not affect the risk of AD in our sample.

Age Factors↗
PubMed2003

[Genetic variation in two forms of the common spadefoot toad Pelobates fuscus (Pelobatidae, Anura, Amphibia) distinguished by genome size].

Genetic differences (presumed 23 loci) between two cryptic forms of Pelobates fuscus, differing in genome size, were examined by means of polyacrylamide-gel electrophoresis. This method allowed to discriminate between these forms. Average genetic distance (DN) between both the forms was equal to 0.311, ranging from 0.055 to 0.563. As a rule, differences within these groups were smaller (0.021-0.388). The data show obvious genetic differentiation between these two cryptic forms of P. fuscus. Differences between these forms and P. syriacus were significantly higher (in average 0.943). Genetic distances in relation to speciation and species concepts are discussed.

Animals↗
PubMed1983

Genetic variation of bluetongue virus serotype 11 isolated from host (sheep) and vector (Culicoides variipennis) at the same site.

Genetic relatedness of 2 strains of bluetongue virus (BTV) serotype 11 that were isolated from the same geographic site--one from host (sheep) and the other from the vector Culicoides variipennis during an enzootic of bluetongue at Bruneau, Idaho, in August 1973--was determined by comparing the oligonucleotide fingerprint analyses of the individual double-stranded RNA segments of the genomes. It was observed that the 2 strains of BTV-11 exhibit considerable differences in their genotypes, the percentage of diversity being different for each of the corresponding RNA species of the 2 strains of BTV-11. These results indicate that more than one genotype of BTV can circulate in juxtaposition in a given geographic site. The observed genotypic diversity might be due to the accumulation of point mutations on specific RNA species or antecedent reassortment of RNA segments between different BTV in nature or both.

Animals↗