树鼩(Tupaia belangeri Wagner)三个亚种的染色体比较研究

本文对中国西南部树鼩(Tupaia belangeri)三个亚种的染色体特征进行了详细比较。结果表明滇西亚种(T.b.chinensis),越北亚种(T.b.tonquinia)和瑶山亚种(T.b.yaoshanensis)的染色体数目均为62:G带和C带基本相似;Ag-NORs的数目相同(4—6个),有相似的分布。应用复制带的技术,确定了雄性树鼩的Y染色体。本结果为树鼩的分类鉴定提供了细胞遗传学依据。     

Isolation and characterization of the first eight microsatellite loci in Gammarus fossarum (Crustacea, Amphipoda) and cross-amplification in Gammarus pulex and Gammarus orinos

We characterized the first microsatellite markers for Gammarus fossarum. Eight loci gave satisfactory amplification patterns in two stream populations (Southern France) with number of alleles ranging from 2 to 10 and expected heterozygosity from 0.076 to 0.857. We performed cross-amplification in two closely related gammarid species, Gammarus pulex and Gammarus orinos. Among the eight tested microsatellite loci, four correctly amplified in G. pulex and three in G. orinos.     

Y-specific microsatellite polymorphisms in a range of bovid species

At least five dinucleotide (CA)n microsatellite repeat arrays have been assigned to the bovine Y-chromosome, with one marker (INRA124) shown to be polymorphic. We describe here the assessment of a panel of four Y-specific microsatellite markers for polymorphism in a range of cattle and related species. It was possible to amplify all the markers in the animals sampled and all showed variation. Three of the microsatellite loci (INRA124, INRA189 and BM861) displayed putative taurine- and zebu-specific alleles which can be useful indicators of male-mediated gene flow in hybrid populations. In the future these microsatellites, in combination with other Y-specific markers should provide a high-resolution Y haplotype system for evolutionary studies in both domesticated cattle and other related species.     

Sex-linked and autosomal microsatellites provide new insights into island populations of the tammar wallaby

The emerging availability of microsatellite markers from mammalian sex chromosomes provides opportunities to investigate both male- and female-mediated gene flow in wild populations, identifying patterns not apparent from the analysis of autosomal markers alone. Tammar wallabies (Macropus eugenii), once spread over the southern mainland, have been isolated on several islands off the Western Australian and South Australian coastlines for between 10 000 and 13 000 years. Here, we combine analyses of autosomal, Y-linked and X-linked microsatellite loci to investigate genetic variation in populations of this species on two islands (Kangaroo Island, South Australia and Garden Island, Western Australia). All measures of diversity were higher for the larger Kangaroo Island population, in which genetic variation was lowest at Y-linked markers and highest at autosomal markers (θ=3.291, 1.208 and 0.627 for autosomal, X-linked and Y-linked data, respectively). Greater relatedness among females than males provides evidence for male-biased dispersal in this population, while sex-linked markers identified genetic lineages not apparent from autosomal data alone. Overall genetic diversity in the Garden Island population was low, especially on the Y chromosome where most males shared a common haplotype, and we observed high levels of inbreeding and relatedness among individuals. Our findings highlight the utility of this approach for management actions, such as the selection of animals for translocation or captive breeding, and the ecological insights that may be gained by combining analyses of microsatellite markers on sex chromosomes with those derived from autosomes.     

Development and mapping of microsatellites from a microdissected BTA 11-specific DNA library

A chromosome-specific library was developed for Bos taurus autosome 11 by chromosome microdissection and microcloning using a bovine primary fibroblast culture, obtained from a t(X;23) heifer, that spontaneously developed a translocation chromosome involving bovine chromosome 11. The library was screened using (AC)12 oligos, positive clones selected, sequenced and primers developed to generate bovine chromosome 11-specific microsatellite markers. This study suggests that chromosome-specific libraries have great potential for development of microsatellite markers for the construction of marker-saturated linkage maps for each chromosome.     

Isolation and characterization of 64 novel microsatellite markers from a fosmid library of female half-smooth tongue sole (Cynoglossus semilaevis)

Microsatellite markers were developed from a fosmid library of female half-smooth tongue sole, Cynoglossus semilaevis. Three hundred eighty-four clones were randomly selected to sequence (double strand reading), and 168 sequences in 143 clones were found to contain microsatellites. Of the 101 primer pairs designed, 64 gave polymorphic polymerase chain reaction products. Based on characterization with 36 individuals, the number of alleles ranged from two to nine. The values of observed and expected heterozygosities varied from 0.06 to 1.00 and from 0.05 to 0.94, respectively. These markers have the potential as tools for population structure evaluation, ecological analyses and linkage map construction.     

Isolation and characterization of new polymorphic microsatellite loci in the mixotrophic orchid Limodorum abortivum L. Swartz (Orchidaceae)

Here, we report the isolation and characterization of 11 polymorphic microsatellites in Limodorum abortivum. Allele variability has been characterized in three populations from Southern Italy and France. The number of alleles ranged from one to six per locus with an average of 3.8 alleles per locus. Observed and expected heterozygosity values ranged from 0.000 to 1.000 and from 0.492 to 0.806, respectively, with striking differences among populations. These microsatellites should be valuable tools for studying fine-scale genetic structure of scattered Limodorum abortivum populations, patterns of relationship with closely related taxa and the evolutionary ecology of its mycorrhizal interactions.     

Difference between evolutionarily effective and germ line mutation rate due to stochastically varying haplogroup size

Within a Y-chromosome haplogroup defined by unique event mutations, variation in microsatellites can accumulate due to their rapid mutation. Estimates based on pedigrees for the Y-chromosome microsatellite mutation rate are 3 or more times greater than the same estimates from evolutionary considerations. We show by simulation that the haplogroups that survive the stochastic processes of drift and extinction accumulate microsatellite variation at a lower rate than predicted from corresponding pedigree estimates; in particular, under constant total population size, the accumulated variance is on average 3-4 times smaller.     

沼泽型水牛Y染色体微卫星标记的筛选与多态性检测

为了研究水牛Y染色体的遗传多样性, 文章以滇东南水牛3个地方群体- 红河(HH)、西双版纳(BN)和普洱(PR)共31头公牛为研究对象, 选取14个家牛Y染色体特异性微卫星标记, 以检测这些标记在水牛Y染色体遗传多样性研究中的可行性。结果表明, 3个标记(INRA008、UMN0103和UMN0504)只有1个等位基因, 表现为单态; 3个标记(UMN1113、UMN0304和BC1.2)均为3个等位基因, 但呈单态; 3个标记(UMN0920、UMN0307和UMN3008)呈现无规律的梯状条带, 所以这9个标记都不适用于水牛的Y染色体遗传多样性研究; 只有5个标记(INRA124、INRA189、BM861、PBR1F1和UMN2001)具有多态性, 表明适用于水牛的Y染色体遗传多样性研究。这5个多态性Y染色体特异微卫星标记在滇东南水牛群体中的平均等位基因数(NA)为2.8000, 平均期望杂合度(He)为0.3998, 基因多样性(GD)为0.4144, 多态信息含量(PIC)为0.3245, Shannon信息熵(SI)为0.5849, 表明滇东南水牛群体的Y染色体具有中等遗传多态性。     

Bacterial artificial chromosome library of Finegoldia magna ATCC 29328 for genetic mapping and comparative genomics

We constructed a bacterial artificial chromosome (BAC) library of Finegoldia magna ATCC 29328 DNA to facilitate further genome analysis of F. magna. The BAC library contained 385 clones with an average insert size of 55 kb, representing a 10.1-fold genomic coverage. Repeated DNA hybridization using primer sets designed on the basis of BAC-end sequences yielded nine contigs covering 95% of the chromosome and two contigs covering 98% of the plasmid. The contigs were localized on the physical map of F. magna ATCC 29328 DNA. A total of 121 BAC-end sequences revealed 103 unique genes, which had not been previously reported for F. magna. The homolog ORF of albumin-binding protein (urPAB), one of the known virulence factors from F. magna, was sequenced and localized on the physical map. Homology analysis of 121 BAC-end sequences revealed that F. magna is most closely related to clostridia, particularly Clostridium tetani. This close relationship is consistent with the recent classification of peptostreptococci based on 16S rRNA sequence analysis. The BAC library constructed here will be useful for the whole genome sequencing project and other postgenomic applications.     

Differential introgression of uniparentally inherited markers in bison populations with hybrid ancestries

Historical hybridization between Bison bison (bison) and Bos taurus (cattle) has been well documented and resulted in cattle mitochondrial DNA (mtDNA) introgression, previously identified in six different bison populations. In order to examine Y chromosome introgression, a microsatellite marker (BYM-1) with non-overlapping allele size distributions in bison and cattle was isolated from a bacterial artificial chromosome (BAC) clone, and was physically assigned to the Y chromosome by fluorescence in situ hybridization. BYM-1 genotypes for a sample of 143 male bison from 10 populations, including all six populations where cattle mtDNA haplotypes were previously identified, indicated that cattle Y chromosome introgression had not occurred in these bison populations. The differential permeability of uniparentally inherited markers to introgression is consistent with observations of sterility among first generation hybrid males and a sexual asymmetry in the direction of hybridization favouring matings between male bison and female cattle.     

Comparative mapping of a region on chromosome 10 containing QTL for reproduction in swine

Several quantitative trait loci (QTL) for important reproductive traits (age of puberty, ovulation rate, nipple number and plasma FSH) have been identified on the long arm of porcine chromosome 10. Bi-directional chromosome painting has shown that this region is homologous to human chromosome 10p. Because few microsatellite or type I markers have been placed on SSC10, we wanted to increase the density of known ESTs mapped in this region of the porcine genome. Genes were chosen for their position on human chromosome 10, sequence availability from the TIGR pig gene indices, and their potential as a candidate gene. The PCR primers were designed to amplify across introns or 3'-UTR to maximize single nucleotide polymorphism (SNP) discovery. Parents of the mapping population (one sire and seven dams) were amplified and sequenced to find informative markers. The SNPs were genotyped using primer extension and mass spectrometry. These amplification products were also used to probe a BAC library (RPCI-44, Roswell Park Cancer Institute) for positive clones and screened for microsatellites. Six genes from human chromosome 10p (AKR1C2, PRKCQ, ITIH2, ATP5C1, PIP5K2A and GAD2) were mapped in the MARC swine mapping population. Gene order was conserved within these markers from centromere to telomere of porcine chromosome 10q, as compared with human chromosome 10p. Four of these genes (PIP5K2A, ITIH2, GAD2 and AKR1C2), which map under QTL, are potential candidate genes. Identification of porcine homologues near important QTL and development of a comparative map for this chromosome will allow further fine- mapping and positional cloning of candidate genes affecting reproductive traits.