Biomedical subjects
Publications and source records attributed to L A Zhivotovskiĭ.
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.
Variation of 13 morphometric wing characters in relation to temperature of development was studied in two sibling species Drosophila melanogaster and D. simulans. Three principal components that accounted for 73% of variation of these characters were identified. The first component was interpreted as general wing size, while the second and third components described wing shape. Temperatures of maximal wing size and temperatures corresponding to the highest values of the third principal component (proximal-distal ratio) were different in the species studied. In each of the species, reaction norm curves of the three-principal components were different, indicating qualitative differences between reaction norms of characters belonging to the same organ. Variances of both general wing size and shape were different at different temperatures. Variance of general wing size was lower at intermediate temperatures and higher at high and low temperatures. Correlations between wing measurements were significantly different at different temperatures.
Stabilizing selection for a set of morphometric wing traits was combined with directional selection for increased expression of radius incompletus (ri) mutation of Drosophila melanogaster. Three experimental regimens were used: directional and stabilizing selection (stabilized lines); directional selection (unstabilized lines); no selection (control lines). The dynamics of two fitness-associated parameters (coefficient of fluctuating asymmetry and population size) was registered during the experiment. At the end of experiment, selection competitive ability test was carried out. The competitive indices did not significantly differ under various treatments, while fluctuating asymmetry was significantly lower in stabilized than in unstabilized lines. Average population size was greater in stabilized lines as compared to the unstabilized ones. The possible causes for these differences are discussed.
The effects of interaction of artificial directional and stabilizing selection were studied using a recessive mutation of Drosophila melanogaster radius incompletus which causes interruption of the second longitudinal wing vein (L2). The character under directional selection was the length of the proximal segment of L2; stabilizing selection was conducted for a complex of morphometric wing characters. Three experimental designs in three replications were used: 1) directional and stabilizing selection; 2) directional selection; 3) unselected controls. The dynamics and variation of the character under directional selection was shown to be different in the stabilized and unstabilized lines. Coefficient of variation which increased in the unstabilized lines remained at the same level in the stabilized lines and in the controls. The results are in agreement with those of the previous experiment, where directional selection was conducted for a behavioral trait, which suggests general character of the relationships observed.
An approach to the investigation of the evolution of quantitative traits on the basis of analysis of two-locus marginal systems dynamics has been developed. It has been shown that under stabilizing selection the "quasi-stationary" state is quickly reached and maintained continuously. The "quasi-stationary" state is characterized by small changes in allele frequencies and by linkage disequilibrium that significantly decreases genotypic variance. Equations defining the role of linkage disequilibrium in the stationary state of mutation-selection balance are derived.
Population size as a measure of population fitness was assayed in laboratory lines of Drosophila melanogaster subjected to directional selection for positive photoactivity and stabilizing selection for a complex of metric wing characters. Three experimental designs were used: directional and stabilizing selection (DS); directional selection (D); unselected controls (C). Population size increased under all three experimental designs. The population size of DS and C lines as well as the rate of increase of the DS lines were higher as compared to the D lines. The results suggest that stabilizing selection maintains population fitness at the higher level.
Explore the source record for details and available documents.
The selection for a single additively inherited quantitative character is studied using computer models of 3 types: 1) all the individuals had the same viability, and the paratypic deviation does not depend on their genotype; 2) differential viability of genotypes is taken into account with respect to a number of heterozygous loci; 3) differential paratypic deviation is estimated, it is introduced like viability in the model 2. Two types of trancation selection, stabilizing and directed, under the selection coefficient of approximately 0.5 are studied. There are studied dynamics of genotypic (omega2gamma) and phenotypic (omega2phi) variances, the heritability index and it estimates (for the correlation progeny-parent--rho; for the regression progeny-parent--b; for half-sibses--v), and the non-equilibrium of a population for the models. The number of generation was 10; the population number in every generation was 200; the number of loci in the main experiment was 10.h2 values were calculated in the progeny before selection (p1, b1, v1) and after selection (p2, b2, v2). It is shown that stabilizing selection results in the formation of balanced gene complexes; the rate of decreasing omega2phi depends on the genetic length of a chromosome region in which genes, determining the character, are located, and not on the number of genes. The distribution of a character under directed selection depends on the type of the model. p2, b2, and v2 values are the worst. The best is the b1 value. It is concluded that the problem of predicting the selection effect using statistical estimates of heretability is connected with the problem of investigation of population heterogeneity and integrating their genetical structure.
Explore the source record for details and available documents.