Yu. P. Altukhov

DNA polymorphism in population genetics

In the review, the literature evidence on DNA polymorphism obtained in the last 10–15 years using various molecular-genetic methods is summarized. All main types of DNA variation are considered but attention is focused on those extensively used in population genetics. The areas of using DNA markers are outlined and the limitations of their potential in analyzing genetic processes in populations are discussed. Particular emphasis is placed on the relationship between the earlier developed biochemical genetics based on protein polymorphism analysis and modern molecular population genetics based on DNA polymorphism. The possible role of selection in maintaining DNA variation is considered.

Genetically Determined Subdivision of Human Populations with Respect to the Risk of Breast Cancer in Women

Analysis of 21 polymorphic sites in nine tumor-suppressor genes revealed associations between specific genotypes and the high risk of sporadic forms of breast cancer. Malignant tumors were shown to appear in 30‐ 35% of cases. Much evidence suggest that the functional state of the BRCA1 and BRCA2 genes determines breast cancer development in women [1, 2]. The highpenetrance mutations of these genes in heterozygous state lead to a significant proportion of familial cancer forms [3]. However, some experimental data suggest that the level of penetrance of these mutations is not stable and depends on other genetic factors. In particular, the allelic state of a polymorphic site in RAD51 gene influences the penetrance of a deletion mutation in the BRCA2 gene [4]. The risk of tumors in specific ethnic groups is also dependent on the allelic states of various genes. For example, the risks of breast cancer differ significantly in Ashkenazi Jews and Icelander carriers of “pathogenic” mutations in BRCA1 and BRCA2 [5, 6]. This suggests that phenotypic expression of mutations in BRCA1 and BRCA2 genes depends on the allelic states of other genes. Among the latter, the candidate genes are primarily the genes whose products interact with BRCA1 and BRCA2 proteins [7, 8].

Genetic differentiation of pink salmon oncorhynchus gorbuscha Walbaum in the Asian part of the range

Genetic variation at 19 enzyme (including 11 polymorphic) and 10 microsatellite loci was examined in the population samples of odd-and even-broodline pink salmon from the southern part of Sakhalin Island, Southern Kuril Islands, and the northern coast of the Sea of Okhotsk. The estimates of relative interpopulation component of genetic variation for the allozyme loci, per broodline, were on average 0.43% (GST), while over the microsatellite loci it was 0.26% (the ϑST coefficient, F-statistics based on the allele frequency variance), and 0.90% (the ρST coefficient, R-statistics based on the allele size variance). The values of interlinear component constituted 2.34, 0.31, and 1.05% of the total variation, respectively. Using the allozyme loci, statistically significant intralinear heterogeneity was demonstrated among the regions, as well as among the populations of southern Sakhalin. Multidimensional scaling based on the allozyme data demonstrated regional clustering of the sample groups, representing certain populations during the spawning run or in different years. Most of the microsatellite loci examined were found to be highly polymorphic (mean heterozygosity > 0.880). The estimates of interlinear, interregional, and interpopulation variation over these loci in terms of ϑST values were substantially lower than in terms of ρST values. Regional genetic differentiation, mostly expressed at the allozyme loci between the populations from the northern Sea of Okhotsk and the Sakhalin and Kuril group of populations, was less expressed at the microsatellite loci. The differentiation between these regions observed can be considered as the evidence in favor of a large-scale isolation by distance characterizing Asian pink salmon. It is suggested that in pink salmon, low genetic differentiation at neutral microsatellite loci can be explained by extremely high heterozygosity of the loci themselves, as well as by the migration gene exchange among the populations (the estimate of the gene migration coefficient inferred from the “private” allele data constituted 2.6 to 3.4%), specifically, by the ancient migration exchange, which occurred during postglacial colonization of the range

Genetic divergence in pink salmon introduced into the European North of Russia: Microsatellite and allozyme variation analysis

The 1985 introduction into the European North of Russia resulted in the formation of a large stock of pink salmon of the odd-year broodline. To assess the divergence of the new population and the role of various microevolutionary factors, variation of four microsatellite loci and fifteen genes encoding proteins (allozymes) in samples of fish, running for spawning in rivers of the new area, and in samples from the donor population of the Ola River (Magadan region). In the generations 8 and 9 of the introduced pink salmon of the odd-year line, the genetic diversity (the number of alleles and the mean heterozygosity) both at allozyme and at microsatellite loci was significantly lower, than that in the donor population. The explanations of the decline in diversity are discussed. The first evidence for spatial genetic divergence in transplanted fish within the new area has been obtained; the divergence level may be comparable with that characteristic of native populations.

Far Eastern Mullet Mugil soiuy Basilewsky (Mugilidae, Mugiliformes): The Genetic Structure of Populations and Its Change under Acclimatization

The introduction of Far Eastern mullet (pilengas) in the Azov Sea in the 1970s–1980s has resulted in the formation of a self-reproducing commercial population. We have carried out a comparative population-genetic analysis of the mullet from the native (Primorye, the Sea of Japan basin) and the new (The Azov Sea basin) ranges. Genetic characteristics of three Primorye and three Azov local samples were studied using electrophoretic analysis of 15 enzymes encoded by 21 gene loci. In the Azov mullet, the initial heterozygosity characteristic of the donor population was preserved while the genotype and the allele compositions changed; the changes included a 1.9-fold reduction in the percentage of polymorphic loci and 1.5-fold reduction in the mean number of alleles per locus. The genetic differences between the Azov and the Primorye sample groups were highly significant. In the native range, no genetic differentiation among the mullet samples from different areas was found (Gst = 0.42%), whereas in the Azov Sea basin, the samples from spatially isolated populations (ecological groups) exhibited genetic differences (Gst = 1.38%). The genetic divergence of the subpopulations and the excess of heterozygotes at some loci in the Azov mullet suggest selection processes that formed genetically divergent groups associated with the areas of different salinity in the new range. The salinity level is assumed to be the most probable factor of local differentiating selection during fast adaptation and naturalization of the introduced mullet.

Genetic Changes in Pink Salmon Oncorhynchus gorbuscha Walbaum during Acclimatization in the White Sea Basin

Genetic parameters of pink salmon introduced into the White Sea basin in 1985 and 1998 were compared to the corresponding parameters of the donor population from the Ola River (Magadan oblast). The detected genetic differences indicate that colonization of a new area is accompanied by impoverishment of the gene pool of the native population. This effect was particularly marked in the odd-year broodline of pink salmon introduced in 1985. The probable causes of these genetic changes are discussed.

Interspecific genetic variability of the oyster mushroom Pleurotus ostreatus as revealed by allozyme gene analysis

Allozyme variation in natural populations of basidiomycete fungus Pleurotus ostreatus (88 individuals) from three regions of central Russia was studied. The species was shown to have 92.86% of polymorphic allozyme loci and expected heterozygosity He = 0.49. The mean number of alleles per locus was 3.5. The genetic differences among populations were supported by F-statistics (FST = 0.750). The low level of inbreeding (FIS = 0.018) suggests that the P. ostreatus populations are panmictic, and the main reproduction mode involves basidiospores dispersing at long distances. Using cluster analysis, geographically isolated populations and intersterile groups were differentiated within the complex P. ostreatus species.

Allozyme heterozygosity, metabolic rate, sexual maturation rate, and longevity.

The results of detailed analysis of interspecific correlations between allozyme heterozygosity, standard metabolic rate, rate of sexual maturation, longevity and linear body size are presented (Fig. 1). The purpose of this work was to determine key casual relationships by means of partial correlation analysis. It was found that the relationship between heterozygosity and metabolic rate lies in the basis of correlations shown in Fig. 1, whereas the genetic determination of the other three characters was mediated by this relation. The highly significant negative correlation between the standard metabolic rate and the age of the first reproduction was demonstrated for the first time. The problem set here follows logically from the results of investigations carried out in the late 20th century [1‐3]. Comparative biometrical analysis of 77 species of animals and 30 species of arboreal plants have shown that the individual genome heterozygosity, age of the first reproduction, longevity, and linear body size are related to one another by highly significant correlations [1, 2]. The analysis of partial correlations have uncovered key causal relationships: a high individual heterozygosity determines high rates of development and sexual maturation and early age of the first reproduction while decelerating the post-reproduction growth and reduces the lifespan [1, 2].

Species-Specific Random Amplified Monomorphic DNA

Intra- and interspecific variability of total DNA isolated from haploid megagametophytes of coniferous species was examined using polymerase chain reaction with random primers. Based on this technique, one can with certainty detect heterozygosity at gene loci carrying null alleles and thus reveal cryptic intraspecific genetic variation. Large population samples were used. Along with random amplified polymorphic DNA, i.e., widely known fragments (amplicons) polymorphic within a species, we found invariant loci lacking individual or geographic variability but differentiating species within genera and other taxa. This DNA was termed RAMD (random amplified monomorphic DNA) to distinguish it from polymorphic DNA. Our findings suggest that genetic monomorphism of species and the dual structure of the eukaryotic genome can be detected at the DNA level as was previously shown for protein gene markers.

Hybridization between Atlantic Salmon Salmo salar L. and Brown Trout S. trutta L. upon Artificial Propagation

Samples of Salmo salar and S. trutta were examined in 12 Russian fish hatcheries. With protein markers, hybrids of the two species were found in three hatcheries of the Baltic Sea basin. Some fishes had a phenotype intermediate between theS. salar and S. trutta phenotypes by morphological traits, but did not differ genetically from one of the parental species. Possible consequences of hybridization and ways to prevent it are discussed.