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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Chicken W: a genetically uniform chromosome in a highly variable genome.
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Chicken W: a genetically uniform chromosome in a highly variable genome.

机译：Chicken WITH：高度可变的基因组中遗传统一的染色体。

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The Y chromosome of organisms with male heterogamety is expected to show reduced levels of genetic diversity, because the effective population size is one-fourth that of autosomes. However, studies in mammals, flies, and plants show that Y chromosome diversity is lower than expected even when differences in effective population size are taken into account. This may be explained by skewed reproductive success among males, leading to low male effective population size, or by a strong role of selection in shaping levels of nucleotide diversity in nonrecombining chromosomes. We tested these hypotheses in a system with female heterogamety by estimating nucleotide diversity in the female-specific W chromosome of the domestic chicken by resequencing of 7,643 base pairs in 47 birds from 10 highly divergent breeds. The screening revealed only one single segregating site, which is in sharp contrast to our previous observation, using a similar panel of birds of, on average, one segregating site every 39 base pairs in autosomal sequence. When taking sex-specific mutation rates and differences in effective population size into account, the observed degree of W chromosome polymorphism is 28-fold lower than expected for the frequency of segregating sites and 13-fold lower than expected for estimates of nucleotide diversity (autosomes, 6.5 x 10(-3); W, 7.0 x 10(-5)). We note that selection is the only factor that can explain the reduced diversity in the sex-limited chromosome irrespective of mode of reproduction or whether there is male or female heterogamety. Reduced variability in female-specific W chromosomes is not easily explained by sexual selection.
机译：具有男性异性配子的生物的Y染色体有望显示出较低的遗传多样性水平，因为有效种群的大小是常染色体的四分之一。但是，对哺乳动物，果蝇和植物的研究表明，即使考虑有效种群大小的差异，Y染色体的多样性也低于预期。这可能是由于男性生殖成功偏向，导致男性有效种群数量偏低或选择对非重组染色体核苷酸多样性水平形成的强烈影响而造成的。我们通过对来自10个高度不同品种的47只鸟中的7,643个碱基对进行重新测序来估计家鸡雌性特异性W染色体中的核苷酸多样性，从而在雌性异配子系统中测试了这些假设。筛选仅显示了一个单一的分离位点，这与我们先前的观察结果形成了鲜明的对比，使用的是类似的鸟群，在常染色体序列中平均每39个碱基对就有一个分离位点。当考虑到性别特异性突变率和有效种群数量的差异时，观察到的W染色体多态性比分离位点的频率低28倍，比核苷酸多样性估计的低13倍（常染色体） ，6.5 x 10（-3）; W，7.0 x 10（-5））。我们注意到选择是唯一可以解释性别受限的染色体多样性降低的因素，而不论繁殖方式或是否存在雄性或雌性异配子。女性特定的W染色体变异性降低，很难通过性别选择来解释。

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