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At least 1,027 records · Page 57Linked to original sources
PubMed1998

Genetic variation of phytate phosphorus utilization from hatch to three weeks of age in broiler chicken lines selected for incidence of tibial dyschondroplasia.

Ability to utilize dietary phytate P was evaluated in 1,387 broiler chicks of 45 sire and 180 dam families, by feeding a corn-soybean base diet supplemented with no inorganic P and a low level of Ca. These chicks were the progeny of high and low incidence of tibial dyschondroplasia (TD) selected divergently for 11 generations and a nonselected control line. Chicks from the control line utilized phytate P better than those from the high or low lines in terms of livability, mortality, and growth performance. Chicks did not differ in mortality and body weight between the high and low lines. Variation in livability and mortality was greater among lines than among families, whereas families accounted for a greater part of variation than lines in body weight. Dams accounted for a slightly larger proportion of variation than sires in traits studied. Genetic selection for improved utilization of dietary phytate P could be effective.

Animal Feed↗
PubMed1996

Genetic variation in yellow fever virus: duplication in the 3' noncoding region of strains from Africa.

The nucleotide sequences of three regions of the genomes of 13 yellow fever (YF) virus isolates were determined to define genetic variation and evolution of the virus. Phylogenetic trees generated from sequences of either the 5' terminal 1320 nucleotides of the genome, 754 nucleotides from the NS4A and NS4B genes, or the 3' terminal 511 nucleotides were very similar and contained minor differences. Overall, these results suggested that there were at least four major genotypes of YF virus, including one in Central/East Africa, one in West Africa, and two in South America. Examination of the 3' noncoding region (3'NCR) showed that only West African strains had a 3'NCR of 511 nucleotides while strains from Central/East Africa and South America had shorter 3'NCRs (443-469 nucleotides) due to the absence of YF specific repeat sequences (RYFs). Central/East African strains have two RYFs and West African strains have three RYFs while South American strains only have one copy of the RYF. It is speculated that duplication of the RYF took place in West Africa subsequent to the presumed introduction of YF virus into South America. Thus, both tick-borne (Mandl et al., J. Virol. 65, 4070-4077, 1991 and Wallner et al., Virology 213, 169-178, 1995) and mosquito-borne flaviviruses have variable 3'NCRs.

Africa↗
PubMed1996

Genetic markers and quantitative genetic variation in Medicago truncatula (Leguminosae): a comparative analysis of population structure.

Two populations of the selfing annual Medicago truncatula Gaertn. (Leguminoseae), each subdivided into three subpopulations, were studied for both metric traits (quantitative characters) and genetic markers (random amplified polymorphic DNA and one morphological, single-locus marker). Hierarchical analyses of variance components show that (1) populations are more differentiated for quantitative characters than for marker loci, (2) the contribution of both within and among subpopulations components of variance to overall genetic variance of these characters is reduced as compared to markers, and (3) at the population level, within population structure is slightly but not significantly larger for markers than for quantitative traits. Under the hypothesis that most markers are neutral, such comparisons may be used to make hypotheses about the strength and heterogeneity of natural selection in the face of genetic drift and gene flow. We thus suggest that in these populations, quantitative characters are under strong divergent selection among populations, and that gene flow is restricted among populations and subpopulations.

Biological Evolution↗
PubMed1999

Conservation implications of genetic variation in three rare species endemic to Florida rosemary scrub.

Habitat conversion and fire suppression during the last 50 yr have greatly reduced and altered Florida scrub vegetation, resulting in threats to the persistence of its unique flora. As part of a larger conservation project, we investigated patterns of isozyme variation in three rare perennial scrub plants with overlapping ranges endemic to Florida rosemary scrub on the Lake Wales Ridge. All three species have low levels of genetic variation, comparable to or lower than those generally reported for rare plants with restricted geographic ranges. Liatris ohlingerae has more than twice the expected heterozygosity of the other two species, with little population differentiation. In contrast, Hypericum cumulicola has highly differentiated populations with little apparent interpopulation gene flow and heterozygote deficiencies indicative of inbreeding. Eryngium cuneifolium, the species with the narrowest range and fewest populations, has intermediate values for genetic parameters. Although the three species have narrow and overlapping geographic ranges and similar habitat specificity, we discuss how optimal conservation of each species differs.

Journal Article↗
PubMed2004

Left ventricular mass in relation to genetic variation in angiotensin II receptors, renin system genes, and sodium excretion.

BACKGROUND: In the European Project On Genes in Hypertension (EPOGH), we investigated in 3 populations to what extent left ventricular mass (LVM) was associated with genetic variation in the angiotensin II receptors type 1 (AGTR1 A1166C) and type 2 (AGTR2 G1675A) while accounting for possible gene-gene interactions with the angiotensin-converting enzyme (ACE D/I) and angiotensinogen (AGT -532C/T) polymorphisms. METHODS AND RESULTS: We randomly recruited 221 nuclear families (384 parents, 431 offspring) in Cracow (Poland), Novosibirsk (Russia), and Mirano (Italy). Echocardiographic LVM was indexed to body surface area, adjusted for covariates, and subjected to multivariate analyses using generalized estimating equations and quantitative transmission disequilibrium tests in a population-based and family-based approach, respectively. For AGTR1 and AGTR2, there was no heterogeneity in the phenotype-genotype relations across populations. LVM index was unrelated to the AGTR1 A1166C polymorphism. In men, in the population- and family-based analyses, the allelic effects of the AGTR2 polymorphism on LVM index differed (P=0.01) according to sodium excretion. In women, this gene-environment interaction did not reach statistical significance. In untreated men, LVM index (4.2 g/m2 per 100 mmol) and left ventricular internal diameter (0.73 mm/100 mmol) increased (P<0.02) with higher sodium excretion in the presence of the G allele with an opposite tendency in A allele carriers. The ACE D/I polymorphism, together with the ACE genotype-by-sodium interaction term, significantly and independently improved the models relating LVM index to the AGTR2 polymorphism and the AGTR2 genotype-by-sodium interaction. CONCLUSIONS: The present findings support the hypothesis that in men the AGTR2 G1675A and the ACE D/I polymorphisms independently influence LVM and that salt intake modulates these genetic effects.

Adolescent↗
PubMed1982

Sex-limited genetic variation in a mouse salivary protein.

This report describes a gene which influences the electrophoretic mobility of a protein in the salivas of adult mice. Three categories of phenotype have been observed: the two single-banded types, F (Fast) and S (Slow), and the two-banded type, SF (Slow-Fast), with the two bands represented in varying proportions. All females, regardless of age or strain, and all males before puberty show only the F phenotype. Males of the BALB/c and C57BL/6J strains show the F phenotype throughout puberty and adult life, whereas males of the C3H/St and C57BL/KsJ strains show the SF phenotype in puberty and the S phenotype in adult life. We have designated this variation the sex-limited saliva pattern (Ssp). The results from genetic crosses indicate that the variation among the strains is determined by an autosomal locus, Ssp, with two alleles, SspS and SspF, where SspS is dominant to SspF. Testosterone treatment can accelerate the acquisition of the S type in males of the strains C3H/St and C57BL/KsJ and also induces that phenotype in C3H/St females and C57BL/6J males. Thus it appears that the observed strain-specific differences reflect a genetic variation in androgen levels and/or androgen sensitivity rather than variation in a structural gene.

Animals↗
PubMed2002

Genetic variation of oaks ( Quercus spp.) in Switzerland. 3. Lack of impact of postglacial recolonization history on nuclear gene loci.

Quercus petraea, Quercus pubescens and Quercus robur are closely related and interfertile white oaks native to Switzerland. The three species are known to share identical cpDNA haplotypes, which are indicative of the postglacial recolonization history of populations. Only two haplotypes are common in Switzerland. We compared variation of cpDNA and of isozymes in 28 oak populations from Switzerland in order to assess the impact of the postglacial population history on current genetic structures of nuclear controlled isozyme gene loci. Species delineation was based on Principal Component Analysis of leaf morphological traits. The species status of populations was reflected at isozyme gene loci, but differentiation between populations with different cpDNA haplotypes and hence different recolonization history was very low at enzyme gene loci for all species. Thus, glacial and postglacial population history was not reflected at nuclear gene loci on the temporal and spatial scale covered by the present study. Extensive gene flow through pollen among populations is likely to have blurred a previously existing genetic differentiation at biparentally inherited gene loci that possibly evolved in the different glacial refugia of the above mentioned cpDNA haplotypes.

Alleles↗
PubMed1997

Genetic variation at five STR loci in subpopulations living in Turkey.

Five short tandem repeat (STR) systems HumVWA, HumTH01, HumCD4, HumF13B and HumFES were investigated in 2 subpopulations living in Turkey (Laz Turks and Kurds). The population genetic data were compared to a Turkish population sample from the Adana area. A closer genetic relationship was found to the Laz Turks than to the Kurdish sample which was also confirmed by phylogenetic tree reconstruction with seven populations from three major ethnic groups (Caucasian, Asian and African). In contrast to the Laz and Adana populations the Kurdish sample showed relatively low heterozygosity values and deviations from Hardy-Weinberg equilibrium in four of the five systems.

Alleles↗
PubMed1999

Sex ratios and genetic variation in a functionally androdioecious species, Schizopepon bryoniaefolius (Cucurbitaceae).

Androdioecy, coexistence of hermaphrodites and males, is an extremely rare breeding system in angiosperms. In the present study, Schizopepon bryoniaefolius (Cucurbitaceae) was confirmed to be functionally androdioecious based on observations of floral and pollen morphology and bagging experiments. Six out of the 11 studied populations consisted of only hermaphrodites, while the other five populations were androdioecious and the frequencies of males were consistently lower than those of hermaphrodites (5.5-28.3%). To understand the consequences of an androdioecious breeding system, genetic variation was estimated using four polymorphic allozyme loci. The degree of genetic differentiation among 11 populations was high (G(ST) = 0.688). Inbreeding coefficients (F(IS)) for all loci significantly deviated from zero. In particular, the F(IS) values averaged across the polymorphic loci in hermaphrodite populations were close to unity, suggesting that hermaphrodites are predominantly selfing in the absence of males. A significant negative correlation was found between the frequencies of males and inbreeding coefficients, indicating that outcrossing rates depend on the population sex ratio.

Journal Article↗
PubMed2003

Population genetic variation in genome-wide gene expression.

Evolutionary biologists seek to understand which traits display variation, are heritable, and influence differential reproduction, because such traits respond to natural selection and underlie organic evolution. Selection acts upon individual differences within a population. Whether individual differences within a natural population include variation in gene expression levels has not yet been addressed on a genome-wide scale. Here we use DNA microarray technology for measuring comparative gene expression and a refined statistical analysis for the purpose of comparing gene expression levels in natural isolates of the wine yeast Saccharomyces cerevisiae. A method for the Bayesian analysis of gene expression levels is used to compare four natural isolates of S. cerevisiae from Montalcino, Italy. Widespread variation in amino acid metabolism, sulfur assimilation and processing, and protein degradation-primarily consisting of differences in expression level smaller than a factor of 2-is demonstrated. Genetic variation in gene expression among isolates from a natural population is present on a genomic scale. It remains to be determined what role differential gene expression may play in adaptation to new or changing environments.

DNA Transposable Elements↗
PubMed2006

Naturally occurring genetic variation in the age-specific immune response of Drosophila melanogaster.

Immunosenescence, the age-related decline in immune response, is a well-known consequence of aging. To date, most studies of age-related changes in immune response focused on the cellular and physiological bases of this decline; we have virtually no understanding of the genetic basis of age-related changes in the immune system or if indeed such control exists. We used 25 chromosome substitution lines of Drosophila melanogaster derived from a natural population to address three questions: (i) How is the function of the innate immune system influenced by age? (ii) Is there a genetic basis for phenotypic variation in immune response at different ages? (iii) Is there a genetic basis for differences in the way that age influences the immune function? Virgin females from each line were assayed for immune response using clearance of infection with Escherichia coli at 1 and 4 weeks of age. We found significant genetic variation among lines in immune response at each age. Unexpectedly, when averaged across all lines, the immune response actually improved with age. However, there was significant variation in the effect of age on immune response with 11 lines showing improvement, nine lines showing no change and five exhibiting a decline with age. There was no genetic correlation of immune response across ages suggesting that different loci contribute to variation in immune response at each age. The genetic component of the variation in immune response increased with age, a pattern predicted by the mutation accumulation model of senescence. However, this increase in variation resulted in part from the improvement of the immune response in some lines with age. Thus the observed changes in genetic variation in immune function with age are not entirely explained by the mutation accumulation model.

Aging↗
PubMed1991

Genetic variation in the stress response: susceptibility to experimental allergic encephalomyelitis and implications for human inflammatory disease.

Glucocorticoids that are released from the adrenal glands in response to stress can have profound effects on the immune system. Here, Don Mason illustrates how genetic variation in the magnitude of such a response can determine susceptibility to an experimental autoimmune disease in rats and discusses the implications for susceptibility to inflammatory diseases in humans. He also addresses the possible long-term effects of glucocorticoids on the balance between the cell-mediated and the humoral aspects of immunity and how this balance may influence the temporal development of an immune reaction.

Animals↗