Population genetics of tunas

Population genetic studies on tunas are reviewed. These studies have focused on phylogenetic reconstructions, species identifications and stock delineation, and have used tools ranging from blood group and allozyme analysis to PCR-aided examination of mitochondrial DNA variation. Both allozyme and mtDNA approaches show tunas in the genus Thunnus to be very closely related to one another, but also indicate that the two presently recognized subspecies of northern bluefin tuna, Thunnus thynnus thynnus and T. t. orientalis , in fact may be worthy of species status. These techniques also permit the unequivocal recognition of specimens, which is not always possible on morphological grounds. However, it is arguable that, until recently, tunas have not received their due attention from geneticists given their commercial significance and the need for information on stock structure to ensure sustainable management. This may be because tunas are known to be highly vagile and therefore levels of population differentiation are expected to be low. None the less, population subdivision has been recorded in several species (skipjack, yellowfin, albacore), although this tends to be on a broad (intra- or inter-oceanic) rather than on a more local scale. New molecular tools, including the PCR-based analyses of nuclear genes and microsatellite loci, are yielding new, highly polymorphic markers, and will enable more powerful analyses of stock structure than have hitherto been possible.     

Population genetics study of hemoglobinopathies in Uzbekistan. II. Population dynamics of hemoglobinopathies

It was shown that on comparing variability of selective neutral genetic marker systems with that of the beta-thalassemia system for the populations of different hierarchical level, the relative importance of selection and genetic drift could be evaluated. The genetic differentiation of the beta-thalassemia gene frequencies in elementary populations (villages) could be solely explained by genetic drift. On the other hand, the differentiation of district populations (the sizes of the populations being 10(6] for beta-thalassemia gene frequencies could be explained by selection forces. This is supported by the fact that the genetic distances and FST values are only significant for the beta-thalassemia gene and not for the neutral genetic systems, when the district populations are compared.     

Population genetics of the HRAS1 minisatellite locus.

Several years ago it was reported that rare HRAS1 VNTR alleles occurred more frequently in U.S. Caucasian cancer patients than in unaffected controls. Such an association, in theory, could be caused by undetected population heterogeneity. Also, in a study clearly relevant to this issue, it was recently reported that significant deviations from Hardy-Weinberg equilibrium exist at this locus in a sample of U.S. Caucasians. These considerations motivate our population genetic analysis of the HRAS1 locus. From published studies of the HRAS1 VNTR locus, which classified alleles into types, we found only small differences in the allele frequency distributions of samples from various European nations, although there were larger differences among ethnic groups (African American, Caucasian, and Oriental). In an analysis of variation of rare-allele frequencies among samples from four European nations, most of the variance was attributable to molecular methodology, and very samples from four European nations, most of the variance was attributable to molecular methodology, and very little of the variance was accounted for by nationality. In addition, we showed that mixture of European subpopulations should result in only minor deviations from expected genotype proportions in a Caucasian database and demonstrated that there was no significant deviation from Hardy-Weinberg equilibrium in our HRAS1 data.     

Population genetics of freshwater snails

Freshwater snails have attracted the attention of biologists for a long time, because they are intermediate hosts of schistosomes, agents of bilharziases. However, population-genetic studies of freshwater snails have been undertaken only during the past decade, covering topics such as the relative roles of genetic drift and gene flow in subdivided populations and the roles of extinction and recolonization events in determining population structure. Other studies in freshwater snails have investigated the maintenance of sex and the evolution of selling, widening a debate restricted mainly to plant populations. The possible role of parasites in freshwater-snail population genetics has also been investigated.     

植物病原物的群体遗传学

品种单一化、生产密集型和一年多茬的现代农业特点导致病原物呈现出进化速度加快、致病力增强及流行风险增大趋势。深入研究病原物群体遗传学对认识病害的流行、有效选育和使用抗性品种乃至控制病害具有重要意义。文章阐述了植物病原物群体遗传学的研究目标和内容、突变、基因迁移、基因重组、随机遗传漂变和自然选择5大遗传机制在植物病原物进化过程中的作用, 以及目前植物病原物群体遗传学研究的现状。     

植物病原物的群体遗传学

品种单一化、生产密集型和一年多茬的现代农业特点导致病原物呈现出进化速度加快、致病力增强及流行风险增大趋势。深入研究病原物群体遗传学对认识病害的流行、有效选育和使用抗性品种乃至控制病害具有重要意义。文章阐述了植物病原物群体遗传学的研究目标和内容、突变、基因迁移、基因重组、随机遗传漂变和自然选择5大遗传机制在植物病原物进化过程中的作用,以及目前植物病原物群体遗传学研究的现状。     

Population genetics of translational robustness

Recent work has shown that expression level is the main predictor of a gene's evolutionary rate and that more highly expressed genes evolve slower. A possible explanation for this observation is selection for proteins that fold properly despite mistranslation, in short selection for translational robustness. Translational robustness leads to the somewhat paradoxical prediction that highly expressed genes are extremely tolerant to missense substitutions but nevertheless evolve very slowly. Here, we study a simple theoretical model of translational robustness that allows us to gain analytic insight into how this paradoxical behavior arises.     

Population aspects of forensic genetics

The paper presents the methodology of forensic genetics as a synthesis of population genetics and forensic medicine. Main population genetic problems, appearing in calculation of probability statistics and interpretation of the results of forensic genetic investigations, are discussed in detail.     

Population genetics of transgene containment

Several strategies have been proposed for creating transgenic cultivars from which transgene escape to wild relatives would seem unlikely; for example, to impede escape through pollen, a transgene could be inserted into chloroplast DNA (cpDNA), which in many crops is rarely transmitted through pollen. None of these strategies would be failsafe; for example, the rate of cpDNA transmission through pollen may be low but non‐zero in many crops. Here, we study how the probability distribution of escape time depends on the rates of pollen and seed flow from the crop to wild populations, the number and sizes of the wild populations, the selection coefficient for the transgene, and a leakage parameter characteristic of the strategy, for example, the rate of cpDNA transmission through pollen. We find that even with a leakage parameter as small as 10^?3, the probability of escape within as few as 10 generations could be appreciable.