Allele Frequency Patterns Research Articles

Systematic Screening for Polymorphisms in the CYP3A4 Gene in the Chinese Population

Cytochrome P450 3A4 (CYP3A4) is a major CYP enzyme in the liver and intestine. It is involved in the metabolism of over 50% of all drugs currently in use. The present study was designed to determine the genetic basis of CYP3A4 variability. Single nucleotide polymorphism (SNP) analysis of the CYP3A4 gene was performed on 60 healthy Chinese subjects consisting of 20 Han, 30 She and ten Dong subjects, using direct sequencing. Linkage disequilibrium, haplotype inference and Hardy-Weinberg equilibrium were also determined for these samples. A total of 20 SNPs were found in the CYP3A4 gene, including 11 known SNPs and nine novel SNPs. The known SNPs detected in our study were CYP3A4*1B, CYP3A4*1G, CYP3A4*10, CYP3A4*13, CYP3A4*14, CYP3A4*15, CYP3A4*17, CYP3A4*18, rs3091339, rs3091430 and rs28371761, and the novel SNPs were -658 A-->C, G27A (E10K), T48A, G14284A (G167D), A15623G (N191D), C15635A (L196I), T15656C (F203L), G14199A (intron 5) and C15566T (intron 6). The allelic frequencies found in our sample varied from 1-37%. The novel SNPs detected in the CYP3A4 gene suggest that the Chinese population has different patterns of allele frequency compared with other populations. Several SNPs were detected in the CYP3A4 gene. The study of genetic variants in CYP3A4 may have an important significance for the understanding of genotype and phenotype relationships.

Implications of inter-population linkage disequilibrium patterns on the approach to a disease association study in the human MHC class III

There is presently much interest in utilizing patterns of linkage disequilibrium (LD) to further genetic association studies. This is particularly pertinent in the class III region of the human major histocompatibility complex (MHC), which has been extensively studied as a disease susceptibility locus in a number of ethnic groups. To date, however, few studies of LD in the MHC have considered non-Caucasian populations. With the advent of large-scale haplotyping of the human genome, the question of utilizing LD patterns across populations has come to the fore. We have previously used LD mapping to direct an MHC class III association study in a UK Caucasian population. As an extension of this, we sought to determine to what extent the pattern of LD observed in that study could be used to conduct a similar study in a West African Gambian population. We found that broad patterns of LD were similar in the two populations, resulting in similar candidate region delineations, but at a higher resolution, marker-specific patterns of LD and population-dependent allele frequencies confounded the choice of regional tagging SNPs. Our results have implications for the applicability of large-scale haplotype maps such as the HapMap to complex regions like the MHC.

Cytonuclear disequilibria in a spatially structured hybrid zone

A hybrid zone model was developed that uses a stepping-stone model of population structure along with both nuclear and cytoplasmic genotypes to evaluate the effect that migration has on random mating organisms when no selection is present. Numerical simulations indicate that a number of different allele frequency and cytonuclear disequilibrium patterns can be found across the hybrid zone when it has reached equilibrium, and these results are discussed in the context of relative migration rates of the two sexes and the two source populations. The importance of numbers of subpopulations sampled, census time, and the persistence of pure species individuals into the hybrid zone are also discussed. Although this model does not consider selection or assortative mating in the hybrid zone, it should provide a useful baseline for evaluating joint cytonuclear genetic data from a structurally complex hybrid zone.

Nonsynonymous SNPs: validation characteristics, derived allele frequency patterns, and suggestive evidence for natural selection

We experimentally investigated more than 1,200 entries in dbSNP that would change amino-acids (nsSNPs), using various subsets of DNA samples drawn from 18 global populations (approximately 1,000 subjects in total). First, we mined the data for any SNP features that correlated with a high validation rate. Useful predictors of valid SNPs included multiple submissions to dbSNP, having a dbSNP validation statement, and being present in a low number of ESTs. Together, these features improved validation rates by almost 10-fold. Higher-abundance SNPs (e.g., T/C variants) also validated more frequently. Second, we considered derived alleles and noted a considerably (approximately 10%) increased average derived allele frequency (DAF) in Europeans vs. Africans, plus a further increase in some other populations. This was not primarily due to an SNP ascertainment bias, nor to the effects of natural selection. Instead, it can be explained as a drift-based, progressive increase in DAF that occurs over many generations and becomes exaggerated during population bottlenecks. This observation could be used as the basis for novel DAF-based tests for comparing demographic histories. Finally, we considered individual marker patterns and identified 37 SNPs with allele frequency variance or FST values consistent with the effects of population-specific natural selection. Four particularly striking clusters of these markers were apparent, and three of these coincide with genes/regions from among only several dozen such domains previously suggested by others to carry signatures of selection.

Allelic and haplotypic diversity of HLA‐A, ‐B, ‐C, ‐DRB1, and ‐DQB1 genes in the Korean population

High-resolution human leukocyte antigen (HLA) typing exposes the unique patterns of HLA allele and haplotype frequencies in each population. In this study, HLA-A, -B, -C, -DRB1, and -DQB1 genotypes were analyzed in 485 apparently unrelated healthy Korean individuals. A total of 20 HLA-A, 43 HLA-B, 21 HLA-C, 31 HLA-DRB1, and 14 HLA-DQB1 alleles were identified. Eleven alleles (A*0201, A*1101, A*2402, A*3303, B*1501, Cw*0102, Cw*0302, Cw*0303, DQB1*0301, DQB1*0302, and DQB1*0303) were found in more than 10% of the population. In each serologic group, a maximum of three alleles were found with several exceptions (A2, B62, DR4, DR14, and DQ6). In each serologic group exhibiting multiple alleles, two major alleles were present at 62-96% (i.e. A*0201 and A*0206 comprise 85% of A2-positive alleles). Multiple-locus haplotypes estimated by the maximum likelihood method revealed 51 A-C, 43 C-B, 52 B-DRB1, 34 DRB1-DQB1, 48 A-C-B, 42 C-B-DRB1, 46 B-DRB1-DQB1, and 30 A-C-B-DRB1-DQB1 haplotypes with frequencies of more than 0.5%. In spite of their high polymorphism in B and DRB1, identification of relatively small numbers of two-locus (B-C and DRB1-DQB1) haplotypes suggested strong associations of those two loci, respectively. Five-locus haplotypes defined by high-resolution DNA typing correlated well with previously identified serology-based haplotypes in the population. The five most frequent haplotypes were: A*3303-Cw*1403-B*4403-DRB1*1302-DQB1*0604 (4.2%), A*3303-Cw*0701/6-B*4403-DRB1*0701-DQB1*0201/2 (3.0%), A*3303-Cw*0302-B*5801-DRB1*1302-DQB1*0609 (3.0%), A*2402-Cw*0702-B*0702-DRB1*0101-DQB1*0501 (2.9%), and A*3001-Cw*0602-B*1302-DRB1*0701-DQB1*0201/2 (2.7%). Several sets of allele level haplotypes that could not be discriminated by routine HLA-A, -B, and -DRB1 low-resolution typing originated from allelic diversity of A2, B61, DR4, and DR8 serologic groups. Information obtained in this study will be useful for medical and forensic applications as well as in anthropology.

Evaluation of Y-STR variation in Bosnian and Herzegovinian population

Eight Y-STR polymorphisms (DYS19, DYS385, DYS389I, DYS389II, DYS390, DYS391, DYS392 and DYS393) were analyzed in the samples of 181 unrelated males from Bosnia and Herzegovinia. Observed STR allelic frequency pattern and locus diversity values in Bosnians and Herzegovinians correspond closer to neighboring southeastern European populations than previously reported (mostly western) European populations. One hundred and five haplotypes were identified and 78 haplotypes (74.3%) appeared in single copies. The most frequent haplotypes (DYS19–DYS385–DYS389I–DYS389II–DYS390–DYS391–DYS392–DYS393) were 16–14/15–13–31–24–11–11–13 (7.7%), 16–14/15–13–30–24–11–11–13 (7.7%) and 15–14/15–13–31–24–11–11–13 (5.5%). Total haplotype diversity was 0.9820 ± 0.0040.

Y chromosome STR polymorphisms in a Serbian population sample

Eight Y chromosome short tandem repeat (STR) polymorphisms (DYS19, DYS385, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393) were analyzed in the sample of 114 unrelated males living in Serbia. A general STR allelic frequency pattern in Serbians corresponds to other European populations with the exception of loci DYS19, DYS389II and DYS385. Out of ninety identified haplotypes, 74 (64.91%) appeared in single copies. The most frequent haplotypes (DYS19–DYS385–DYS389I–DYS389II–DYS390–DYS391–DYS392–DYS393) 16-14/15-13-31-24-11-11-13 and 15-15/19-12-28-23-10-12-12 were found in four copies (3.51%). Total haplotype diversity was 0.9947 ± 0.0021.

Identification of single nucleotide polymorphisms in the tumor necrosis factor (TNF) and TNF receptor superfamily in the Korean population

The tumor necrosis factor (TNF) and TNF receptor (TNF-TNFR) superfamily plays crucial roles in immune regulation and host immune responses. The superfamily has been also associated with many immune-mediated diseases such as asthma, rheumatoid arthritis, inflammatory bowel disease, and diabetes. In order to investigate genetic variants of the TNF-TNFR superfamily, a total of 63 known single nucleotide polymorphisms (SNPs) in the coding region (cSNPs) of the TNF-TNFR superfamily genes were selected from the public SNP database. Among 63 cSNPs tested in this study, only 24 SNPs (38%) were validated to be polymorphic in the Korean population by primer extension-based SNP genotyping. By means of the new enhanced single strand conformational polymorphism (SSCP) method, we also identified a total of 78 SNPs, including 48 known SNPs and 30 novel SNPs, in the 44 human TNF-TNFR superfamily genes. The newly discovered SNPs in the TNF-TNFR superfamily genes revealed that the Korean population had very different patterns of allele frequency compared with African or white populations, whereas Korean allele frequencies were highly similar to those of Asian (correlation coefficient r = 0.88, p < 0.046). A higher similarity of allele frequency was observed between Korean and Japanese populations ( r = 0.90, p < 0.001). The validated SNPs in the TNF-TNFR superfamily would be valuable for association studies with several immune-mediated human diseases.

Y chromosome haplotypes in Albanian population from Kosovo

Eight Y chromosome short tandem repeat (STR) polymorphisms (DYS19, DYS385, DYS389I, DYS389II, DYS390, DYS391, DYS392, and DYS393) were analyzed in the sample of 117 unrelated Albanian males living in Kosovo. A general STR allelic frequency pattern in the Albanian population from Kosovo corresponds to other European populations. Fourty six haplotypes were observed in single copy. The most frequent haplotypes were (DYS19-DYS385-DYS389I-DYS389II-DYS390-DYS391-DYS392-DYS393) 14-11/11-13-29-24-11-13-13 (10.26%), 14-14/17-12-28-24-10-11-12 (9.40%), 13-16/18-13-30-24-10-11-13 (9.40%), and 14-17/17-13-31-24-10-11-13 (9.40%).

Conservation of Population Diversity of Pacific Salmon in Southeast Alaska

We analyzed intraspecific variation in selected biological characteristics of five species of Pacific salmon Oncorhynchus spp. in southeast Alaska and adjacent areas of Canada with a particular interest in describing the variation among populations and suggesting conservation priorities to preserve existing variation. We identified traits that showed high levels of among-population variation, evaluated the interspecific consistency of variation patterns, and noted the relationship of these traits to potential adaptive variation. In addition, we graphically identified populations with distinctive phenotypic and demographic characteristics as outliers from the distribution of mean values of traits taken from populations throughout the region. We also reviewed allozyme surveys to identify populations that differed in terms of the geographic clustering patterns of allele frequencies. Approximately 9,000 salmon populations occur in the study area, and sufficient data were available from 2,062 (23%) of them to analyze at least one characteristic. We identified 47 populations represented by adequate data sets that have distinctive characteristics. An additional 35 populations, represented by limited samples or unusual nominal traits, may be regionally distinctive. Of the 47 adequately sampled, distinctive populations, 22 met our criteria for conservation consideration: (1) high potential for adaptive variation (including distinctive run timing), (2) a distinctive trait combined with high spawner abundance or allozyme frequencies that diverge from geographic clustering patterns, and (3) more than one distinctive characteristic or freshwater habitat shared with other distinctive populations. Freshwater habitats for 6 of those 22 populations are located in watersheds that do not have restrictive land use designations and warrant the highest conservation priority.

Y chromosome STRs in Croatians

Eight Y chromosome short tandem repeat (STR) polymorphisms (DYS19, DYS388, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393) were analyzed in the sample of 457 unrelated Croatian men. A general STR allelic frequency pattern in Croatians corresponds to other European populations with the exception of the loci DYS19 and DYS389II. The most frequent DYS19 allele was 16, while at the DYS389II the most frequent were alleles 30 and 31. The most frequent Y chromosome haplotype (16-13-13-31-24-11-11-13) was found in 33 individuals (7.22%). One hundred and seventy-four haplotypes (38.07%) were observed in single copies.

Determination of a kinship system using ancient DNA, mortuary practice, and historic records in an upper Canadian pioneer cemetery

AbstractRecovered and amplified ancient DNA (aDNA), from a historically documented 19th century Upper Canadian pioneer cemetery produced genotypes that were used to infer a past societal kinship system. While the results from multiplex short tandem repeat (STR) amplifications showed an unreliable polymerase chain reaction (PCR) product, a single locus HUMTH01 analysis yielded reproducible data and an allelic frequency pattern not statistically different from modern populations. Mitochondrial (mt) DNA HVR II data showed that a combined cemetery database exhibited reduced haplotype diversity indicators, as well as clusters of probable maternally related burials. The chronological persistence and replacement of mtDNA clusters approximately every two generations suggests a patrilineal/patrilocal kinship structure from a virilocal burial program for the Harmony Road cemetery. Through the integration of the aDNA analysis with archaeological material culture, historic records, and other ethnohistoric sources of information, this conclusion is supported. In this study persisting patrilineally inherited surnames act as a surrogate for aDNA Y‐chromosome haplotype analysis. These results suggest that aDNA applications on aggregate skeletal collections where sparse, or no ethnological or historical documentation exists, may result in incorrect population history inferences if the presence of a kinship interment bias is not considered. Copyright © 2003 John Wiley &amp; Sons, Ltd.

The mode of evolution of molecular markers in populations of house mice under artificial selection for locomotor behavior.

A complete understanding of the mode of evolution of molecular markers is important for making inferences about different population genetic parameters, especially because a number of studies have reported patterns of allelic variation at molecular markers that are not in agreement with neutral evolutionary expectations. In the present study, house mice (Mus domesticus) from the fourteenth generation of a selection experiment for increased voluntary wheel-running activity were used to test how selection on a complex behavior affects the distribution of allelic variation by examining patterns of variation at six microsatellite and four allozyme loci. This population had a hierarchical structure that allowed for simultaneous testing of the effects of selection and genetic drift on the distribution of allelic variation by comparing observed patterns of allele frequencies and estimates of genetic divergence at multiple hierarchical levels to expectations under models of neutral evolution. The levels of genetic divergence among replicate lines and between selection groups, estimated from microsatellite data or pooled microsatellite and allozyme data, were not significantly different from expectations under neutral evolution. Furthermore, the pattern of change of allele frequencies between the base population and generation 14 was largely in agreement with expectations under neutral evolution (although the PGM locus exhibited a pattern of change within populations that was difficult to explain under neutral evolution). Overall the results generally provide support for the neutral evolution of molecular markers.

Molecular genetic variation in the East Midlands, England: analysis of VNTR, STR and Alu insertion/deletion polymorphisms

Background: Short tandem repeats (STRs) and variable number of tandem repeats (VNTRs) have been used successfully in disease analysis and studies of human evolution and population genetic diversity. However DNA-based comprehensive population genetic studies of the East Midlands, England are limited. Subjects and methods: To enlarge our understanding of genetic variation in the East Midlands, a study was conducted on five regional populations: north-west Derbyshire, north-east Derbyshire, south Derbyshire, Nottinghamshire and Leicestershire. Blood samples were collected from donors whose ancestors had lived in the region for at least three generations. Seven VNTRs (MS1 (D1S7), MS31 (D7S21), MS43A (D12S11) and YNH24 (D2S44), D1S80, APOB, YNZ22 (D17S5)), six STRs (HumTHO1, HumVWA31A, HumF13A01, HumFESFPS, HumCSF1PO, HumTPOX) and six Alu insertion/deletion polymorphisms (TPA25, ACE, PV92, F13B, APO, D1) were analysed in approximately 500 individuals. Allele or bin frequencies were calculated using gene counting and fixed bin methods. The chi-square method and exact tests were used to assess Hardy-Weinberg equilibrium. Genetic distances were calculated using Nei's DA method and correspondence analysis was used to assess population affinities. Results: The overall pattern of allele frequencies was similar to many European and UK populations for a number of genetic systems. Overall heterogeneity was observed for five loci: MS43A, MS31, HumF13A01, HumFESFPS and HumTHO1. Twenty-three of 190 pairwise population comparisons were also statistically significant at the 5% level. Average molecular genetic system heterozygosity was 1.5 times higher than observed with conventional blood group systems. GST values for molecular systems were also higher than conventional systems (0.012 vs 0.005) and suggest a low to moderate level of differentiation. Conclusion: The allele frequency spectrum and inter-population comparisons show that there is significant genetic variation in the five contiguous regional populations of the East Midlands. Some of this variation may be due to local geographical barriers, genetic drift and possibly the settlement patterns of Continental European invaders.

Single nucleotide polymorphisms in innate immunity genes: abundant variation and potential role in complex human disease.

Under selective pressure from infectious microorganisms, multicellular organisms have evolved immunological defense mechanisms, broadly categorized as innate or adaptive. Recent insights into the complex mechanisms of human innate immunity suggest that genetic variability in genes encoding its components may play a role in the development of asthma and related diseases. As part of a systematic assessment of genetic variability in innate immunity genes, we have thus far have examined 16 genes by resequencing 93 unrelated subjects from three ethnic samples (European American, African American and Hispanic American) and a sample of European American asthmatics. Approaches to discovering and understanding variation and the subsequent implementation of disease association studies are described and illustrated. Although highly conserved across a wide range of species, the innate immune genes we have sequenced demonstrate substantial interindividual variability predominantly in the form of single nucleotide polymorphisms (SNPs). Genetic variation in these genes may play a role in determining susceptibility to a range of common, chronic human diseases which have an inflammatory component. Differences in population history have produced distinctive patterns of SNP allele frequencies, linkage disequilibrium and haplotypes when ethnic groups are compared. These and other factors must be taken into account in the design and analysis of disease association studies.

Impact of a population bottleneck on symmetry and genetic diversity in the northern elephant seal

Abstract The northern elephant seal (NES) suffered a severe population bottleneck towards the end of the nineteenth century. Theoretical expectations for the impact of population bottlenecks include the loss of genetic diversity and a loss of fitness (e.g. through a disruption of developmental stability); however, there are few direct demonstrations in natural populations. Here, we report on the comparison of archive samples collected prior to and following the NES population bottleneck. Measures of genetic diversity show a loss of variation consistent with expectations and suggest a strong disruption in the pattern of allele frequencies following the bottleneck. Measures of bilateral characters show an increase in fluctuating asymmetry.

FINE-SCALE POPULATION STRUCTURE IN THE WOOD FROG (RANA SYLVATICA) IN A NORTHERN WOODLAND

We investigated the genetic structure of wood frog (Rana sylvatica) populations in a woodland habitat around Lake Itasca, Minnesota, USA. Based on published studies of wood frog movement patterns, we expected to find genetic differentiation at inter-population distances exceeding a few kilometers. We sampled 10 populations separated by 95 m to 9.6 km. Of five microsatellite loci developed for a study of R. sylvatica in North Dakota, only three were polymorphic in the Itasca sample. We found some evidence for statistically significant differences among populations, with the greatest magnitude estimates of FST derived from comparisons involving the most isolated populations. The smallest geographic distance associated with a statistically significant genetic difference was 1070 m, but most populations were very similar in allele frequencies, even at distances greater than several kilometers. Small sample sizes and the small number of loci limited the strength of any conclusions regarding fine-scale population structure. Itasca populations were significantly different than populations from Nelson County, North Dakota, a distance of over 200 km, with FST estimated at about twice the largest pairwise estimates among Itasca samples. Even at this distance, however, there were substantial similarities in the overall pattern of allele frequencies at four of the five loci.

Population genetic study of the STR loci (HUMCSF1PO, HUMTPOX, HUMTHO1, HUMLPL, HUMF13A01, HUMF13B, HSFESFPS and HUMVWA) in North Indians

Background: Highly polymorphic genetic markers like short tandem repeats (STRs) have been used successfully in disease analysis and studies of human evolution and population genetic diversity. However, DNA-based population genetic studies of Indian populations are limited. Subjects and Methods: To enlarge our understanding of genetic variation in Indian populations, a population genetic study was carried out on Jat Sikh (Punjab, North India) individuals ( n = 150) using a battery of the STR loci. The STR loci analysed by means of PCR amplification followed by electrophoresis and silver staining included HUMCSF1PO, HUMTPOX, HUMTHO1, HUMLPL, HUMF13A01, HUMF13B, HUMFESFPS and HUMVWA loci. Results: The overall pattern of allele frequencies was similar to many Caucasian and Indian populations and heterozygosity varied from 65% (HUMLPL) to 85% (HUMVWA). For all eight loci, no deviations from the Hardy-Weinberg equilibrium hypothesis were detected. Significant differences were observed between Jat Sikhs and African, Chinese and Indian tribes. The mean exclusion probability ranged from 35% to 70%, and the power of discrimination from 81% to 93%, indicating the potential of these loci for forensic and paternity investigations. Conclusion: The allele frequency spectrum, heterozygosity, probability of exclusion, match probability and discrimination probability estimates show interesting variation and suggest the usefulness of these loci for anthropogenetic, paternity and forensic investigations in Indian populations.

Classical polymorphisms in Berbers from Moyen Atlas (Morocco): genetics, geography, and historical evidence in the Mediterranean peoples

Background : Mediterranean population relationships have recently been reviewed through the analysis of classical and DNA markers. The differentiation between Berbers and Arabic-speakers to the south, and the genetic impact of the seven centuries of Muslim domination in the Iberian Peninsula have been among the most interesting questions posed in these studies. Aim : The present study seeks to assess the degree of genetic affinity between the two main population groups of Morocco: Berbers and Arabic-speakers. Data from the Berber study population were also compared with published information on 20 circum-Mediterranean groups. Subjects and methods : A Berber sample of 140 indviduals from Moyen Atlas (Morocco) has been characterized using 15 classical markers (ABO, Duffy, MNSs, Rh, ACPl, AKl, ESD, GLOI, 6-PGD, PGMl, GC, HP, PI, PLG and TF). Results : Allele frequencies in the Berbers fit well into the general southern Mediterranean ranges, albeit with some peculiarities, such as the high FY*A, ACPl*C, and PI*S values. The general pattern of relationships among Mediterranean peoples tested by genetic variance analysis was compatible with a north-south geographical differentiation. Spatial auto-correlation analysis in the different geographical regions of the Mediterranean reveals that the highest degree of association between allele frequencies and geographical distances corresponds to the western (41% of significant correlograms) and northern Mediterranean populations (33%). When only southern Mediterranean groups were considered, the degree of geographical structure considerably decreases (11% of significant correlograms). Conclusions : The different loci studied revealed close similarity between the Berbers and other north African groups, mainly with Moroccan Arabic-speakers, which is in accord with the hypothesis that the current Moroccan population has a strong Berber background. Differences in the spatial pattern of allele frequencies also are compatible with specific population histories in distinct Mediterranean areas, rather than general population movements across the whole region.

Microsatellites reveal high levels of gene flow among populations of the California squid Loligo opalescens.

Information on the extent of genetic differentiation among populations of the squid Loligo opalescens is crucial for the conservation of this commercially utilized species. We analysed six highly variable microsatellite loci in 11 collections of L. opalescens from different locations and spawning seasons to estimate the relative influence of two major evolutionary forces, gene flow and genetic drift. Microsatellite allele frequency patterns suggest that gene flow prevents population differentiation in L. opalescens. Tests for genetic differentiation showed homogeneity of the samples with an overall FST/RST of 0.0028/-0.0013. Genetic uniformity among samples from different year classes indicates that allele frequency patterns in L. opalescens are relatively stable over time. However, a more complete and detailed picture of fine-scale allele frequency shifts in this species will require a systematic microsatellite analysis of local populations over consecutive spawning cycles.