Medico-genetic study of the population of the Samarkand region. II. Population-genetic description of 4 kishlaks of the Urgut district]

This report is a second one in a series of works devoted to the medico-genetical screening of Uzbekistan populations. The paper comprises the results of the analysis of the populational structure of one of the village councils (soviets) of the Urgut District of the Samarkand Region. The main parameters of the population studied were as follows: total number 1529 persons, the average number of inhabitants of one village--328. The proportion of the inhabitants studied--56%, the average number of persons per family--5.22; the average period between subsequent generations--30-35 years, the gametic index--0.8, the inbreeding coefficient inferred from pedigrees--0.018899--0.00781, Fst = 0.03577, the average genetic distanse according to Edwards--0.0231-0.0671. The distribution of Mendelian markers (ABO, Rh, Hp and Ptc) was studied. The observed ratio between a high degree of inbreeding and a relatively low extent of isolation of populations permits to explain satisfactorily the distribution and frequencies of hereditary pathology in the Urgut District of the Samarkand Region pointed out in the previous report.     

Genetic microstructure in two Spanish cat populations. II: gametic disequilibrium and spatial autocorrelation

In a previous publication, we described some aspects of the microgenetic structure of two Spanish cat populations (in Barcelona and Alicante). In the present study, the possible existence ofgametic disequilibrium and spatial genetic structure for these populations, at the coat colour pattern and length genes O, A, T D, L, S and W, was analyzed. There was little gametic disequilibrium between pairs of these loci, despite certain pairs that showed significant systematic gametic disequilibrium (a-d and O-S), which appears to show the action of natural selection on domestic cat populations. Nevertheless, we believe that the major cause of the small amount of gametic disequilibrium found was probably a combination of gene drift and gene flow. The results obtained here were clearly in disagreement with those of Hedrick (1985), who concluded that epistatic selection was the cause of the gametic disequilibrium that he found in cat populations. We also found that although Hardy-Weinberg equilibrium could not be demonstrated, the gametic disequilibrium statistics were not affected by this fact, adding credence to the estimates obtained. We found no genetic spatial structure inside the city of Barcelona, as shown by analysis of the spatial autocorrelation of the individual loci, and analysis of the coordinates of the two first axes of a multidimensional scale. However, some gametic disequilibrium statistics showed certain spatial patterns, which leads us to consider the possibility of several evolutionary processes acting upon some of Barcelona's cat colonies.     

High Differentiation among Eight Villages in a Secluded Area of Sardinia Revealed by Genome-Wide High Density SNPs Analysis

To better design association studies for complex traits in isolated populations it''s important to understand how history and isolation moulded the genetic features of different communities. Population isolates should not “a priori” be considered homogeneous, even if the communities are not distant and part of a small region. We studied a particular area of Sardinia called Ogliastra, characterized by the presence of several distinct villages that display different history, immigration events and population size. Cultural and geographic isolation characterized the history of these communities. We determined LD parameters in 8 villages and defined population structure through high density SNPs (about 360 K) on 360 unrelated people (45 selected samples from each village). These isolates showed differences in LD values and LD map length. Five of these villages show high LD values probably due to their reduced population size and extreme isolation. High genetic differentiation among villages was detected. Moreover population structure analysis revealed a high correlation between genetic and geographic distances. Our study indicates that history, geography and biodemography have influenced the genetic features of Ogliastra communities producing differences in LD and population structure. All these data demonstrate that we can consider each village an isolate with specific characteristics. We suggest that, in order to optimize the study design of complex traits, a thorough characterization of genetic features is useful to identify the presence of sub-populations and stratification within genetic isolates.     

A complex medico-genetic study of West Siberian populations. I. Formulation of a problem. Goals and objectives of the study. Population genetic characteristics of Northern Khanty

Purposes and tasks of the complex medical and genetic study of West-Siberian inhabitants were formulated. Demographic parameters for the North Khanty inhabitants, such as size, dynamics of the tertiary sex ratio, marriage structure and migration processes were presented. Mating and intrapopulation migration patterns are determined by spatial subdivision, because of the vast territory and the traditional way of life, and by isolation by distance. Index of the isolocal endogamy equals to 0.364. The portion of mixed marriages is 22.7% and that of the gametic contribution of immigrants - 7.3%. Inbreeding coefficient by isonymy is 0.00097. Effective population size of the five subpopulations studied as a whole is 25% of their total number.     

Ethnic and Geographical Aspects of the Prevalence of the Polymorphic Variants of Genes Associated with Tuberculosis

Specificity of the structure of gene pools of different ethno-territorial groups of the human population can underlie the epidemiological features of the spread of tuberculosis (TB) and the structure of the genetic component of the susceptibility to the disease. The variability of 62 genetic variants potentially associated with the risk of the development of TB in the Russian population of the city of Tomsk has been studied and the differentiation of various ethno-territorial groups of the world by these markers has been assessed. The studied sample comprised 445 Russian residents of the city of Tomsk without bronchopulmonary pathology. For comparison, the data on the variability of the genetic markers of interest in 26 populations from the 1000 Genomes Project was involved. In the Tomsk population, only the ancestral allele was found for seven of the 58 SNPs studied; the allele frequencies for 36 markers were within the limits of the values seen in other European populations; for 12 SNPs, the observed frequencies were closer to populations with a significant Mongoloid component. By the total of the SNPs, the Tomsk population, despite the geographical distance from the rest of the European populations, did not differ from them (in genetic distances and G_st statistics), although it had some features of the gene pool. Intergroup differentiation of the world populations by these SNPs reflects mainly interracial differences. The greatest differences in the genetic structure between the studied populations were seen for the markers localized in intergenic regions. Statistically significant differences were found when comparing the levels of the average expected heterozygosity between groups of “L4 carrier populations” of mycobacteria and “non-L4” populations, which indicates the impact of the prevalence of different pathogenic lineages of M. tuberculosis on the formation of population specificity of the allelic frequencies.     

A Comparison of the Genetic Infrastructure of the Ye''Cuana and the Yanomama: A Likelihood Analysis of Genotypic Variation among Populations

A general procedure is described for measuring and testing population differences in gametic frequencies. The total dispersion among populations is subdivided in hierarchical fashion. The multiple-locus treatment is simply the sum of the single-locus analyses, provided gametic equilibrium obtains among the loci. In the event that gametic equilibrium does not obtain, correlations among loci need to be dealt with.—The analysis is then used to examine the genetic infrastructure of two Indian tribes from South America, the Ye'cuana (Makiritare) and the Yanomama. From historical evidence, we may identify several "clusters" of villages within each tribe. The demographic and cultural practices affecting village formation and the maintenance of peer integrity are rather different in these tribes, however, and lead us to postulate rather different patterns of genetic variation among villages. Analyses of five codominant two-allele loci, four dominant two-allele loci and two complex loci (with four codominant haplotypes each) demonstrate that Yanomama clusters are more disparate than Ye'cuana clusters, as would have been predicted on sociocultural grounds.     

Genetic structure of Dagestan populations: a study of 11 Alu insertion polymorphisms

We examined genetic variation in nine populations of Dagestan using 11 autosomal Alu insertion polymorphisms to investigate the genetic structure of indigenous groups and to assess their genetic relationship with world populations. Genetic differentiation among mountain inhabitants (Gsr = 2%) is comparable to that for European populations. Traces of genetic drift are detectable only for endogamous and small Ando-Dido-speaking ethnic groups, and they coincide with the most linguistically diverse region of Dagestan. Multidimensional scaling analyses among West Eurasian populations revealed that mountain inhabitants of Dagestan are closely related to Anatolian and Cyprus Turks. Thus our frequency data are consistent with the available Y-chromosome data, according to which the Middle East and the Caucasus share a considerable portion of the gene pool. Overall, our results corroborate the initially suggested genetic contribution of Middle Eastern populations to Caucasus populations.     

Endogamy and variation in blood pressure levels in Croatian island isolates

Blood pressure variation was investigated among populations inhabiting islands and peninsula of Middle Dalmatia, Croatia. The number of previous anthropological studies pointed to isolation and different genetic population structure in this environmentally fairly homogeneous area. Variation in blood pressure (systolic and diastolic) among the populations of the islands of Brac, Hvar, Korcula, and the Peljesac peninsula was assessed at three levels involving village populations, regional (western and eastern) populations and the entire island populations. The blood pressure data were collected from 3834 adult individuals inhabiting 37 rural communities and were adjusted for age and body mass index. Variation in blood pressure levels existed among regions and villages. Due to the history of differential settlement, small village sizes and high levels of reproductive isolation, the observed blood pressure variation could be attributed to founder effect, genetic drift and inbreeding. The involvement of genetic factors was tested by relating blood pressure variation among villages to degree of isolation among them. Blood pressure means and proportions of hypertensives increased with endogamy levels in males. In females, this effect could not be observed. However, in both sexes the highest proportions of hypertensives (more than 40%) were found in villages that are most reproductively closed (endogamy greater than 80%). These populations are considered particularly promising for further genetic epidemiological research.     

Marital and migration structure and inbreeding in the Adyg population]

Endogamy and gametic indices for both Russian and Adyg populations living in the Adyg autonomous region of Krasnodar district were determined on different levels of territorial units: village, rural, community (a group of villagers) and rural region. Inbreeding coefficient was estimated for Adyg population and its structure analysed: a random component contributes mostly to the inbreeding coefficient (Fst = 0.00991), non-random component of the inbreeding coefficient being Fis = 0.010009, which testifies to negative marital assortativity among Adygs. Local inbreeding "a" and decline in the inbreeding "phi" coefficient at a distance from 0 to 500 km were calculated using the Malecot's formula: the coefficient "a" was found to be 0.00397, which is in good accordance with the Fst.     

Genetic diversity and multilocus associations in Cunninghamia lanceolata (Lamb.) Hook from The People's Republic of China

Open-pollinated seeds were assayed for allozyme polymorphisms at 24 loci to assess genetic diversity and multilocous associations in 16 populations of Cunninghamia lanceolata (Lamb.) Hook in the People's Republic of China. On average, the percentage of polymorphic loci was 88.0, the number of alleles per locus was 3.0, and the expected heterozygosity was 0.394. The distribution of genetic diversity was not correlated with the geographic and climatic variables of the populations. However, allele frequencies correlated linearly with the mean annual temperature of the populations at Mdh-1, Mdh-2, Mnr-2, Pgi-1, and Skdh-1 and with the altitude of the populations at Aph-4 and 6Pg-2. Of the total gene diversity 6% was attributed to among-population differentiation; 94% resided within populations. Two-locus gametic disequilibria were found in 15 of the 16 populations, and higher-order gametic disquilibria were significant in most populations. The gametic disequilibria did not correlate with geographic and climatic variables. The results suggest that population subdivision, founder effect, occurrence across diverse environments, a mating system dominated by inbreeding, and historical events from 2000 years of cultivation are contributing factors in the generation and maintenance of the multilocus genetic structure in this conifer.     

Analysis of a secondary contact between divergent lineages of brown trout Salmo trutta L. from Duero basin using microsatellites and mtDNA RFLPs

The analysis of 12 microsatellite loci in 16 native populations of Salmo trutta from Duero basin evidenced a strong genetic differentiation in accordance with the existence of two divergent Atlantic mtDNA lineages, Atlantic (AT) and Duero (DU). These lineages were observed spatially segregated mainly in the Lower-course and in the inner part of the basin. Unlike previous isozyme information, microsatellite data suggested a more downstream location of the sharpest genetic divergence in Duero basin and a more complex structure in the inward area. Putative hybrid populations evidenced higher Hardy–Weinberg and gametic disequilibria than pure ones (Pisuerga, Lower-course), not explained by mixture due to differential immigration pattern across the basin. Hybridization indexes suggested a bimodal pattern of hybridization and a higher weight of Pisuerga region in the genetic composition of hybrid samples in accordance with mtDNA data. The results suggested a limited introgression between AT and DU lineages. Taking into account the time of divergence between both lineages, selection and/or genetic incompatibility appeared necessary to explain the genetic structure observed and the ancient location of DU lineage restricted to this area.     

The population structure of rural settlements of Sakha Republic (Yakutia): migration

Migration and gametic structure have been analyzed in rural population of Sakha Republic (Yakutia). The populations studied differ from one another in the migration rate and direction, which are determined by the socioeconomic development of the regions and ethnic composition of settlements. A high rate of long-distance migrations and a low rate of migrations within uluses (districts) are characteristic of regions with well-developed industry and transportation and are more characteristic of immigrant than indigenous populations. In rural regions, migrations within uluses are more prevalent. The gametic structure of the youngest age group does not always correspond to the migration activity of previous generations. The migration effectiveness values (the correspondence of migration flows to the gametic structure depending on the geographic origin of the gametes) are different for men and women.     

The population structure of rural settlements of Sakha Republic (Yakutia): Migration

Migration and gametic structure have been analyzed in rural population of Sakha Republic (Yakutia). The populations studied differ from one another in the migration rate and direction, which are determined by the socioeconomic development of the regions and ethnic composition of settlements. A high rate of long-distance migrations and a low rate of migrations within uluses (districts) are characteristic of regions with well-developed industry and transportation and are more characteristic of immigrant than indigenous populations. In rural regions, migrations within uluses are more prevalent. The gametic structure of the youngest age group does not always correspond to the migration activity of previous generations. The migration effectiveness values (the correspondence of migration flows to the gametic structure depending on the geographic origin of the gametes) are different for men and women.     

The effect of variable frequency of sexual reproduction on the genetic structure of natural populations of a cyclical parthenogen

Cyclical parthenogens are a valuable system in which to empirically test theoretical predictions as to the genetic consequences of sexual reproduction in natural populations, particularly if the frequency of sexual relative to asexual reproduction can be quantified. In this study, we used a series of lake populations of the cyclical parthenogen, Daphnia pulicaria, that vary consistently in their investment in sexual reproduction, to address the questions of whether the ecological variation in investment in sex is detectable at the genetic level, and if so, whether the genetic patterns seen are consistent with theoretical predictions. We show that there is variation in the genetic structure of these populations in a manner consistent with their investment in sexual reproduction. Populations engaging in a high frequency of sex were in Hardy-Weinberg and gametic phase equilibrium, and showed little genotypic differentiation across sampled years. In contrast, populations with a lower frequency of sex deviated widely from equilibrium, had reduced multilocus clonal diversity, and showed significant temporal genotypic deviation.     

Population genetics of the inhabitants of Northern European USSR. II. Blood group distribution and antropogenetic characteristics in 6 villages in Archangel Oblast]

The paper deals with the distribution of genetic markers (systems ABO, MN, Rh (D), Hp, PTC) and a number of demographic (folding of arms, hand clasping, tongue rolling, right- and left-handedness, of the type of ear lobe, of the types of dermatoglyphic patterns) in the inhabitants of 6 villages in the Mezen District of the Archangelsk Region of the RSFSR (river Peosa basin). The data presented in this work were obtained in the course of examination of over 800 persons. Differences in the interpretation of the results of generally adopted methods of statistical analysis of samples from small populations are discussed. Among the systems analysed in one third of all the cases there was a statistically significant deviation from Hardy-Weinberg's ratios. For the MN blood groups and haptoglobins this was caused by the excess of heterozygotes. The test of Hardy--Weinberg's ratios at the level of two-loci phenotypes revealed no statistically significant deviations either in separate villages or in all the villages taken together. The analysis of heterogeneity with respect to markers inherited according to Mendel's law revealed statistically significant differences between villages in all the systems except haptoglobins. A considerable heterogeneity in the distribution of family names, the frequencies of some of them varying from village to village from 0 to 90%. Statistically significant differences between villages were shown for all the anthropogenetic characters except arm folding, hand clasping and right-left-handedness. Considering the uniformity of the environmental pressure in the region examined, the heterogeneity of the population studied is apparently associated with a random genetic differentiation (genetic drift) and, possibly, with the effect of the progenitor.     

Genetic architecture of a small, recently aggregated Aleut population: Bering Island, Russia

The fishing community of Bering Island, located in the Russian Commander Islands off the Kamchatka Peninsula, was originally founded by a small number of Russian soldiers and merchants, along with Aleuts forcibly relocated from the western region of the Aleutian archipelago. The purpose of this study is to characterize the genetic variation of Bering Island inhabitants for autosomal, mitochondrial, and Y-chromosome DNA and classic genetic markers and to investigate the genetic impact of the 19th-century founding and subsequent demographic events on this heterogeneous community. Our results show a loss of diversity among maternal lineages in the Bering Aleut population, with fixation of mtDNA haplogroup D, as revealed by median-joining network analysis and mismatch differences. Conversely, paternal haplotypes exhibit an increase in diversity and the presence of a substantial number of non-Native lineages. Admixture results, based on autosomal STR data, indicate that parental contributions to the mixed Aleut population of Bering are approximately 60% Aleut and 40% Russian. Classic genetic markers show affinities between the Bering Island Aleuts and the other historically founded Aleut communities of St. Paul and St. George in the Pribilof Islands, Alaska. This study demonstrates that the opposing evolutionary forces of genetic drift and gene flow acted on the maternal and paternal lineages, respectively, to shape the genetic structure of the present-day inhabitants of Bering Island.     

Genetic analysis of a population with abnormalities of gene frequencies]

Nineteen out of the 53 blood donors of french village with 241 inhabitants (Cezay Loire) are Rh negative (D--). This discrepancy in the distribution is analysed. 1.--The study of the genetic erythrocyte markers (ABO and Rh system for 158 inhabitants, Kell, Rautenberg, Duffy, Kidd, MNSs, P1 Lutheran, PGM1, PGM2, 6 PGD, AK, ADA, Acid phosphatase systems for 104 inhabitants) show significant abnormal gene frequencies (No. 10%) compared with a control population from Saint-Etienne, for A1, Ms, r, P1 alleles; conversely rare alleles do not seem to exist. HLA system was not tested. 2.--The genetic study led to: a) a demographic study which implied 7840 registrar's certificates and the building up of 1364 families to which the 5096 subjects belonged identified and having lived in Cezay since 1607 (this date corresponds to the earliest registrar's certificate). b) it also led to the analysis of the origin and evolution of the genetic inheritance throughout the 13 generations of known inhabitants. The calculation of the chances of each generation having passed on its genetic material to following generations shows that: Cezay has an integrated population; 30% of the genes are renewed for each generation the average value of each founder can vary according to the various generations but there seems to exist a "founder effect" of the Rh--(D--) having been and lived in the village before 1860. Although they represent 68% of the total population, the tested samples can be contested for certain systems, in its constitution (formation, choice) which prevents from ascertaining the foundation effect observed. The authors underligne the contribution of immunogenetics to the genetics of populations, and show the incidence of the choice of samples in the method used.     

Genetic demographic structure of rural populations of Kyrgyzstan

The genetic demographic parameters of rural populations of Kyrgyzstan have been studied. The rural population of Kyrgyzstan has the following demographic characteristics: (1) it is demographically young (the population mean age is 25-28 years); (2) the sex ratio in reproductive age groups is unfavorable; (3) the fertility is high (5.78-7.68 pregnancies and 4.27-5.20 surviving children per woman of postreproductive age; (4) interethnic marriages are rare (1.0-5.9%), whereas consanguineous marriages are frequent (1.4-12%); (5) Crow's indices are relatively low (I(tot) = 0.24-0.29, I(m) = 0.05-0.13, I(f) = 0.14-0.22); and (6) both male and female contributions of different regions of the republic make unequal contributions to the gametic structure of the population, with the gametic structure varying from generation to generation. Demographic parameters vary in rural populations of different geographic regions and with different ethnic compositions.     

Genetic coadaptation in the chromosomal polymorphism of Drosophila subobscura II. Changes of gametic disequilibrium in experimental populations

Experimental populations were examined for temporal changes of gametic disequilibria between allozyme loci (Lap and Pept-1) and gene arrangements of the O chromosome of Drosophila subobscura (O _st and O ₃₊₄₊₇) under several environmental conditions. In the foundation of the experimental populations a genetic perturbation was carried out in order to test the relevance of the current hypotheses used to explain the allozyme-inversion associations observed in natural populations. Differential changes of gametic disequilibria were detected over generations under the different environmental conditions. Mere mechanical or stochastic factors cannot explain the results and natural selection is probably the major agent generating the detected gametic associations. The observations are interpreted as a proof of coadaptation of D. subobscura inversions.     

Population genetics of the population of the northern European RSFSR. III. Demographic and genetic characteristics of two rural communities of the Pinezhskii District of the Arkhangel'sk Region]

The paper deals with the distribution of genetic markers (systems ABO, Rh, Hp, PTC) and a number of phenotyping traits (folding of arms, hand clasping, tongue rolling, right- and left-handedness, the type of ear lobe, the types of dermatoglyphics patterns) in the inhabitants of 5 villages in the Pinezhsky district of the Arkhangelsky region of the RSFSR. The data presented in this work were obtained in the course of examination of over 900 persons. Among the systems analysed there was a statistically significant deviation from Hardy-Weinberg's equlibrium. It took place in two the least villages. In one case--for ABO blood groups, in another--for Hp system. There are an interesting fact of the excess of heterozygotes 2-1 and some excess of the group 0. Statistically significant differences between villages were shown for four genetic systems. Data on migrations, distribution of gene frequencies and estimated genetic and phenotype distances between villages of the same village community and between two communities suggest, that each village community can be considered as separate subdivided population. Considering the uniformity of the environmental pressure in the region examined, the heterogeneity of the population studied is apparently associated with a random genetic drift.