Low levels of nucleotide diversity in mammalian Y chromosomes
Low levels of nucleotide diversity in mammalian Y chromosomes
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DOI：
10.1093/molbev/msh008
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发表时间：
2004-01-01
影响因子：
10.7
通讯作者：
Ellegren, H
中科院分区：
文献类型：
--
作者：
Hellborg, L;Ellegren, H
性染色体为研究影响遗传多样性的进化力量的相对重要性提供了有用的背景。人类 Y 染色体显示的核苷酸多样性水平为常染色体的 20%，当考虑到有效群体规模和性别特异性突变率的差异时，该水平明显低于预期。为了研究哺乳动物基因组中低水平 Y 染色体变异的普遍性，我们研究了五种哺乳动物的 X (1.1-3.0 kb) 和 Y (0.7-3.5 kb) 染色体基因内含子序列的核苷酸多样性：山猫、狼、驯鹿、牛和田鼠。对于所有物种，Y 上的核苷酸多样性低于 X 上的核苷酸多样性，在山猫、驯鹿和牛的 Y 连锁序列中没有观察到分离位点。对于 X 染色体序列，核苷酸多样性在 1.6 x 10(-4)（山猫）至 8.0 x 10(-4)（田鼠）范围内。当考虑到有效种群规模的差异和雄性突变偏差的程度时，所有五个物种都显示出 Y 染色体变异水平降低的证据。在果蝇和植物以及鸟类雌性特有的 W 染色体中也观察到 Y 染色体变异水平降低。在提出解释性别限制染色体（Y/W）中低水平遗传变异性的不同因素中，我们注意到选择是唯一广泛适用的因素，无论繁殖方式如何以及是否存在男性或女性异配性。
Sex chromosomes provide a useful context for the study of the relative importance of evolutionary forces affecting genetic diversity. The human Y chromosome shows levels of nucleotide diversity 20% that of autosomes, which is significantly less than expected when differences in effective population size and sex-specific mutation rates are taken into account. To study the generality of low levels of Y chromosome variability in mammalian genomes, we investigated nucleotide diversity in intron sequences of X (1.1-3.0 kb) and Y (0.7-3.5 kb) chromosome genes of five mammals: lynx, wolf, reindeer, cattle, and field vole. For all species, nucleotide diversity was found to be lower on Y than on X, with no segregating site observed in Y-linked sequences of lynx, reindeer, and cattle. For X chromosome sequences, nucleotide diversity was in the range of 1.6 x 10(-4) (lynx) to 8.0 x 10(-4) (field vole). When differences in effective population size and the extent of the male mutation bias were taken into account, all five species showed evidence of reduced levels of Y chromosome variability. Reduced levels of Y chromosome variability have also been observed in Drosophila and in plants, as well as in the female-specific W chromosome of birds. Among the different factors proposed to explain low levels of genetic variability in the sex-limited chromosome (Y/W), we note that selection is the only factor that is broadly applicable irrespective of mode of reproduction and whether there is male or female heterogamety.