Differential structuring of human populations for homologous X and Y microsatellite loci.

The global pattern of variation at the homologous microsatellite loci DYS413 (Yq11) and DXS8174 and DXS8175 (Xp22) was analyzed by examination of 30 world populations from four continents, accounting for more than 1,100 chromosomes per locus. The data showed discordant patterns of among- and within-population gene diversity for the Y-linked and the X-linked microsatellites. For the Y-linked polymorphism, all groups of populations displayed high FST values (the correlation between random haplotypes within subpopulations, relative to haplotypes of the total population) and showed a general trend for the haplotypes to cluster in a population-specific way. This was especially true for sub-Saharan African populations. The data also indicated that a large fraction of the variation among populations was due to the accumulation of new variants associated with the radiation process. Europeans exhibited the highest level of within-population haplotype diversity, whereas sub-Saharan Africans showed the lowest. In contrast, data for the two X-linked polymorphisms were concordant in showing lower FST values, as compared with those for DYS413, but higher within-population variances, for African versus non-African populations. Whereas the results for the X-linked loci agreed with a model of greater antiquity for the African populations, those for DYS413 showed a confounding pattern that is apparently at odds with such a model. Possible factors involved in this differential structuring for homologous X and Y microsatellite polymorphisms are discussed.     

Bovine Y chromosome microsatellite polymorphisms

Thirty-eight bovine Y chromosome (BTAY) microsatellites (MS) were assessed for polymorphisms in DNA samples obtained from 17 unrelated bulls. Thirty-three of these microsatellites are new and were used for the construction of a first generation radiation hybrid map for BTAY (Liu et al., 2002). Five MS had been previously reported and were used as positive controls. Fourteen out of 38 MS were found to be polymorphic; the remaining 24 were uninformative among the animals tested. The number of hemizygous loci per MS within individual ranged from two to over 20. Seven MS presented smear- or ladder-like bands, a unique feature for Y chromosome multi-copy hemizygous MS loci. The locus length variance, within individual, ranged from 2 to 42 bp corresponding to the MS with the minimum and maximum number of loci observed, respectively. Within the 14 polymorphic MS, the five pseudoautosomal MS, on average, were more polymorphic (35.3%) than the nine Y-specific MS (19.6%). Haplotypes resulting from combinations of these polymorphic loci will provide a powerful tool for future studies on the origin of domestic cattle and the evolution of bovid species.     

Analysis of five y-Specific microsatellite loci in Asian and Pacific populations

We have analyzed five Y-specific microsatellite loci (DYS388, DYS390, DYS391, DYS394, DYS395) in 17 Asian and Pacific populations representing a broad geographical area and different linguistic families, with an emphasis on populations from mainland and insular Southeast Asia. Analysis of gene diversity indicates that several of the studied populations have experienced substantial genetic isolation, and a reduction in male effective sizes (viz. the Northeast Indian populations Nishi, Adi and the Taiwanese aboriginals). The average values of the F_ST and (_ST statistics indicate a high degree of genetic differentiation among these populations at the five Y-specific markers (F_ST =0.21 and (_ST = 0.33, based on individual loci; F_ST = 0.09 and (_ST = 0.36, based on haplotypes), which conform to the expectation of a fourfold smaller effective size of the Y-linked loci compared with the autosomal loci. Dendrogram and principal coordinates analysis, with few exceptions, show a major separation between mainland and insular populations. Among the mainland populations, the Tibeto-Burman speakers from Northeast India cluster in a well-defined group, supported by high bootstrap values. The Southern Chinese, Northern Thai, So, and Cambodian also are integral to this cluster. The other major cluster is rather heterogeneous and includes, among others, the Austronesian-speaking populations. The Samoans of the Pacific, with a distinctive pattern of allelic distributions, stand as an outlier in the tree and PC representations. Although trends of genetic affinities among ethnically and geographically related populations are evident from the Y-specific microsatellite data, microsatellites are not optimal for deciphering complex migratory patterns of human populations, which could possibly be clarified by using additional and more stable genetic markers. Am J Phys Anthropol 110: 1–16, 1999. © 1999 Wiley-Liss, Inc.     

合浦珠母贝三个养殖群体微卫星遗传多样性

以广东徐闻金碧公司养殖场、广西北海营盘镇养殖场和南海水产研究所海南实验基地3个合浦珠母贝养殖群体为对象,利用8个微卫星位点M1、M2、M3、M4、M5、M6、M7、M8的引物进行了遗传多样性分析.结果表明:8个微卫星标记位点在3个养殖群体中共检测到58个等位基因,观测等位基因数为2～9个,平均有效等位基因数3.72～5.06,平均观察杂合度0.41～0.56,平均期望杂合度0.67～0.75,3个群体的平均多态信息含量PIC值为0.62～0.70,全部为高度多态(PIC≥0.5),表明这几个合浦珠母贝养殖群体目前仍具有较高的遗传多样性,遗传信息丰富,遗传变异大,可以作为良好的育种材料;在这3个养殖群体中,南海水产研究所海南实验基地的养殖群体的遗传多样性最高,广西北海营盘镇养殖群体遗传多样性最低,这一结果可以为今后选择育种、种质保护提供可资借鉴的资料.

Abstract：

By using eight mierosatellite loci (M1, M2, M3, M4, M5, M6, M7 and MS), the genetic diversity of three Pinctada fucata populations from the pearl farms in Xuwen of Guang-dong and Beihai of Guangxi, and from the experimental base of South China Sea Fisheries Re-search Institute in Hainan was studied. A total of fifty eight alleles of these eight microsatellite lo-ci were detected, among which, the observed allele number was 2-9, average effective allele number was 3.72-5.06, average observed population heterozygosity was 0. 41-0. 56, and aver-age observed expected heterozygosity was 0. 67-0. 75. All the three populations had a polymor-phie information content (PIC) of 0. 62-0.70, suggesting their high polymorphism (PIC > 0. 5). Among the three populations, the cultured population from the experimental base of South China Sea Fisheries Institute had the highest polymorphism, and that from Beihai of Guangxi had the lowest one. These results provided useful information for the selective breeding and germplast conservation of P. Fucata.     

Selection on MHC-linked microsatellite loci in sheep populations

Microsatellites within the major histocompatibility complex (MHC) region have received increasing attention as proxy measures of the level of polymorphism at the Mhc genes themselves. We assessed the diversity of microsatellite loci within or in close proximity of the Mhc genes in several breeds of domestic sheep (Ovis aries) and the wild Mouflon (Ovis orientalis musimon). This was compared to variation at other microsatellite loci scattered throughout the sheep genome. Significantly higher number of alleles were observed at the MHC microsatellites. The sheep breeds studied fell into high- and low-diversity group. This grouping is not related to the agricultural use of the breeds, whether for milk, meat or wool. It is, however, correlated with the geographic origins of the breeds. Southern breeds are genetically more diverse than northern breeds. The observed heterozygosity was in most cases lower than Hardy-Weinberg expectations. The potential impact of selective breeding by man on this is discussed. Neutrality tests indicated that for most of the breeds, the distribution of alleles at the MHC-linked microsatellites are more even than would be expected if the genes were neutral and sampled from populations under drift-mutation equilibrium. Hitchhiking due to tight linkage with alleles at the MHC loci that are under balancing selection is proposed as a possible explanation for this pattern.     

Haplotypes of two diallelic Y chromosome loci in the indigenous and migrant populations of Siberia

Two diallelic Y-chromosome markers, the Y Alu polymorphism (YAP) and the T-C transition (Tat), were analyzed in the indigenous (Tuvinian, Buryat, Northern Altaic, and Tatar) and migrant (Slavic) populations of Siberia. A high frequency of the allele C was revealed in several indigenous populations (25-55%) and in Russians (20.8%). The YAP+ allele occurred at a surprisingly high frequency (31.4%) and was completely linked with the C allele in Buryats. The YAP+ chromosome was also found in the Tuvinian population (1.5%). The two diallelic loci showed a marked linkage disequilibrium (D = 92.4%) in the total sample. The YAP-/T and YAP-/C haplotypes prevailed in both indigenous and migrant populations: their respective frequencies were 80.4 and 19.6% in the Slavic population and 71.8 and 19.9%, respectively, in the indigenous one. The YAP+/C (7.8%) and YAP+/T (0.5%) haplotypes were found only in the indigenous population. An appreciable heterogeneity in haplotype frequency distribution between regional subpopulations was revealed in Russians, Tuvinians, and Buryats. The origin and evolution of Y-chromosome lines in Northern Asia are considered.     

Genetic diversity of microsatellite loci in hierarchically structured populations

Microsatellite loci are widely used for investigating patterns of genetic variation within and among populations. Those patterns are in turn determined by population sizes, migration rates, and mutation rates. We provide exact expressions for the first two moments of the allele frequency distribution in a stochastic model appropriate for studying microsatellite evolution with migration, mutation, and drift under the assumption that the range of allele sizes is bounded. Using these results, we study the behavior of several measures related to Wright’s F_ST, including Slatkin’s R_ST. Our analytical approximations for F_ST and R_ST show that familiar relationships between N_em and F_ST or R_ST hold when the migration and mutation rates are small. Using the exact expressions for F_ST and R_ST, our numerical results show that, when the migration and mutation rates are large, these relationships no longer hold. Our numerical results also show that the diversity measures most closely related to F_ST depend on mutation rates, mutational models (stepwise versus two-phase), migration rates, and population sizes. Surprisingly, R_ST is relatively insensitive to the mutation rates and mutational models. The differing behaviors of R_ST and F_ST suggest that properties of the among-population distribution of allele frequencies may allow the roles of mutation and migration in producing patterns of diversity to be distinguished, a topic of continuing investigation.     

Characteristics and frequency of germline mutations at microsatellite loci from the human Y chromosome, as revealed by direct observation in father/son pairs

A number of applications of analysis of human Y-chromosome microsatellite loci to human evolution and forensic science require reliable estimates of the mutation rate and knowledge of the mutational mechanism. We therefore screened a total of 4,999 meioses from father/son pairs with confirmed paternity (probability >/=99. 9%) at 15 Y-chromosomal microsatellite loci and identified 14 mutations. The locus-specific mutation-rate estimates were 0-8. 58x10-3, and the average mutation rate estimates were 3.17x10-3 (95% confidence interval [CI] 1.89-4.94x10-3) across 8 tetranucleotide microsatellites and 2.80x10-3 (95% CI 1.72-4.27x10-3) across all 15 Y-chromosomal microsatellites studied. Our data show a mutational bias toward length increase, on the basis of observation of more repeat gains than losses (10:4). The data are in almost complete agreement with the stepwise-mutation model, with 13 single-repeat changes and 1 double-repeat change. Sequence analysis revealed that all mutations occurred in uninterrupted homogenous arrays of >/=11 repeats. We conclude that mutation rates and characteristics of human Y-chromosomal microsatellites are consistent with those of autosomal microsatellites. This indicates that the general mutational mechanism of microsatellites is independent of recombination.     

Heterogeneity of the Y chromosome in Afro-Brazilian populations

Sixteen biallelic markers (SRY10831a, SRY10831b, SRY4064, SRY2627, 92R7, P2, P3, M34, M9, M3, M2, YAP, M60, M89, M213, M216) located in the nonrecombinant region of the Y chromosome were analyzed in 209 individuals belonging to six Brazilian populations: four Afro-Brazilian populations, one population of white European descendants, and one population of Japanese descendants. The results showed that most of the Y chromosomes of the Afro-Brazilians were from sub-Saharan Africa and that the proportion of Y chromosomes of European origin was greater than that of Y chromosomes of Amerindian origin. No typical African or Amerindian haplogroup was detected among Japanese individuals, and only one white individual showed a typical African haplogroup. Haplogroup P-92R7, which is highly frequent in the Portuguese and Italian populations, was the most frequent among whites (54%), and haplogroup K-M9, which shows wide geographic distribution and is absent in Africa, was the most frequent among Japanese individuals (65.6%). The two semi-isolated Afro-Brazilian populations showed the highest and the lowest genetic diversity, respectively. These differences probably reflect the effect of greater or smaller gene flow between a small isolated group and other populations. These findings show that the process of admixture does not occur homogeneously, with a tendency toward preferential marriages within the ethnic group and a clear direction in unions between European men and Amerindian or African women in the past. The results agree with historical and social data about the formation of the Brazilian population and reveal some of the factors that contribute to its heterogeneity.     

The distribution and frequency of microsatellite loci in Drosophila melanogaster

We report the results of a comprehensive search of Drosophila melanogaster DNA sequences in GenBank for di-, tri-, and tetranucleotide repeats of more than four repeat units, and a DNA library screen for dinucleotide repeats. Dinucleotide repeats are more abundant (66%) than tri- (30%) or tetranucleotide (4%) repeats. We estimate that 1917 dinucleotide repeats with 10 or more repeat units are present in the euchromatic D. melanogaster genome and, on average, they occur once every 60 kb. Relative to many other animals, dinucleotide repeats in D. melanogaster are short. Tri- and tetranucleotide repeats have even fewer repeat units on average than dinucleotide repeats. Our WorldWide Web site (http://www.bio.cornell.edu/genetics/aquadro/aquadro.html) posts the complete list of 1298 microsatellites (≥ five repeat units) identified from the GenBank search. We also summarize assay conditions for 70 D. melanogaster microsatellites characterized in previous studies and an additional 56 newly characterized markers.     

Genetic variation at twentythree microsatellite loci in sixteen human populations

We have analysed genetic variation at 23 microsatellite loci in a global sample of 16 ethnically and geographically diverse human populations. On the basis of their ancestral heritage and geographic locations, the studied populations can be divided into five major groups, viz. African, Caucasian, Asian Mongoloid, American Indian and Pacific Islander. With respect to the distribution of alleles at the 23 loci, large variability exists among the examined populations. However, with the exception of the American Indians and the Pacific Islanders, populations within a continental group show a greater degree of similarity. Phylogenetic analyses based on allele frequencies at the examined loci show that the first split of the present-day human populations had occurred between the Africans and all of the non-African populations, lending support to an African origin of modern human populations. Gene diversity analyses show that the coefficient of gene diversity estimated from the 23 loci is, in general, larger for populations that have remained isolated and probably of smaller effective sizes, such as the American Indians and the Pacific Islanders. These analyses also demonstrate that the component of total gene diversity, which is attributed to variation between groups of populations, is significantly larger than that among populations within each group. The empirical data presented in this work and their analyses reaffirm that evolutionary histories and the extent of genetic variation among human populations can be studied using microsatellite loci.     

B chromosome frequency in yugoslav rye populations

Cytologická analysa 25 populací ?ita z Jugoslavie, které byly vybrány ve Slovinsku, Srbsku a Makedonii, ukázala, ?e ve v?ech analysovaných populacích (100 %) se vyskytovaly B-chromosomy. Po?et p?ítomných B-chromosom? byl nízký, od 1 do 3, p?i ?em? pr?mě rný po?et na jednu rostlinu se pohyboval v rozmezí od 0,13 do 0,97. Pr?měrná ?etnost ?itných rostlin s B-chromosomy byla pro Jugoslavii 27, 10%. ?etnost rostlin s B-chromosomy a pr?měrný po?et chromosom? této kategorie, vzta?ený na jednu rostlinu, byly zna?ně vět?í v aridní oblasti Makedonie ne? v humidní oblasti Slovinska. Rozdíly byly reálné a významné, jak to bylo proká záno biometricky. P?i hodnocení údaj? jiných autor? o populacíoh primitivních asijských ?it bylo zji?těno, ?e frekvence B-chromosom? je ni??í v populacích z oblastí, ozna?ovanýeh jako centra p?vodu tohoto rostlinného druhu (Blízký Východ, Malá Asie) a postupně se jejich frekvence zna?ně zvy?uje s postupem ve směru na vychod (Zabajkali, Korea) i ve směru na západ (Balkánský poloostrov, Jugoslavie). Diskutují se mo?né p?í?iny zvy?ování ?etnosti B-chromosom? v populacich vně center p?vodu ?ita a je zd?razněn význam jejich studia v západoevropských populaeí eh primitivních forem ?ita.     

基于微卫星位点的人工圈养豚鹿亲子关系鉴定

豚鹿属我国国家I级重点保护动物,目前国内野生种群已经灭绝,人工圈养数量少,已极度濒危。成都动物园是国内最大的豚鹿饲养单位,对该园内豚鹿进行亲子鉴定及遗传谱系建立是我国豚鹿拯救工程中一重要环节。本文利用7个微卫星标记对成都动物园27只豚鹿个体进行了基因分型,在母本已知情况下成功鉴定了13对父子关系,其中排除法鉴定8对,似然法鉴定5对且置信度达95%。将亲子鉴定的结果辅以动物园豚鹿圈养的历史记录,我们构建了该园豚鹿的遗传谱系图。本文的研究成果将为后续人工繁殖中亲本雌雄配对的个体选择以及种群的遗传管理提供参考。     

Isolation and characterization of seven tetranucleotide microsatellite loci in mungbean,Vigna radiata

A simple and rapid method for isolating tetranucleotide microsatellites in mungbean, Vigna radiata, based on the 5′‐anchored polymerase chain reaction technique, revealed 15 microsatellite sequences. We report on the characterization of seven polymorphic microsatellite loci in V. radiata. The number of alleles per locus ranged from 2 to 6, whereas the observed heterozygosity ranged from 0 to 0.561. Tetranucleotide markers are useful because they amplify fewer stutter bands thus making scoring easier. These markers will be useful for detecting genetic variation in mungbean varieties for germplasm management and development of the crop.     

TSPY variants in six loci on the human Y chromosome

We have studied the structure, organization, and evolution of the human TSPY gene family by mapping three sequence variants identified through RT-PCR analysis onto genomic clones derived from two different YAC contigs. TSPY gene family members occur in at least six locations on the human Y chromosome, and each cluster contains a unique combination of variants. Our data further suggest that an 18-bp tandem duplication found in TSPY exon 1 originated from an unequal sister chromatid exchange between two tandemly arranged TSPY clusters.