許多年以后男人將會消失,？這是前段時(shí)間科學(xué)界發(fā)現(xiàn)決定男性特征的Y染色體上的基因數(shù)目在不斷減少后出現(xiàn)的一種極端推論，英國研究人員就此表示,，他們進(jìn)行的一項(xiàng)最新研究表明Y染色體不會消失,。
Y染色體是男性所獨(dú)有的、決定男性特征的染色體,。之前有研究發(fā)現(xiàn),，Y染色體上的基因數(shù)目在不斷減少，按此速度推算在約1000萬年后Y染色體將完全消失,，有人因此做出了男人將隨之消失的推論,。
英國倫敦大學(xué)學(xué)院等機(jī)構(gòu)研究人員在新一期美國《國家科學(xué)院學(xué)報(bào)》PNAS上報(bào)告說，這種極端推論是站不住腳的,，對雞的W染色體的分析就可以說明這一點(diǎn),。在雞的遺傳物質(zhì)中，存在一種W染色體,，它是母雞所獨(dú)有的,，其作用與人類男性的Y染色體大致相當(dāng)。研究人員調(diào)查了一些不同種類的雞的遺傳進(jìn)化的情況,，結(jié)果發(fā)現(xiàn),，在斗雞等長期重視雄性特征的雞中，雌斗雞W染色體的確出現(xiàn)了退化,；但是在另一些蛋雞中,，W染色體的功能卻得到了加強(qiáng),。與下蛋相聯(lián)系的是繁殖能力，而繁殖能力對一個(gè)物種來說是至關(guān)重要的,，正是這個(gè)進(jìn)化上的大前提確保了母雞W染色體的持續(xù)存在甚至加強(qiáng),。
進(jìn)行研究的朱迪思·曼克教授說，男性Y染色體的情況也差不多,，雖然Y染色體上的基因在過去不斷減少,，但剩下的部分在生育中發(fā)揮著非常重要的作用，從長期來看Y染色體應(yīng)該不會消失,。（生物谷Bioon.com）
doi:10.1073/pnas.1202721109
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PMID:
W chromosome expression responds to female-specific selection
Hooman K. Moghadama, Marie A. Pointera, Alison E. Wrighta,b, Sofia Berlinc, and Judith E. Mankb,1
The W chromosome is predicted to be subject to strong female-specific selection stemming from its female-limited inheritance and therefore should play an important role in female fitness traits. However, the overall importance of directional selection in shaping the W chromosome is unknown because of the powerful degradative forces that act to decay the nonrecombining sections of the genome. Here we greatly expand the number of known W-linked genes and assess the expression of the W chromosome after >100 generations of different female-specific selection regimens in different breeds of chicken and in the wild ancestor, the Red Jungle Fowl. Our results indicate that female-specific selection has a significant effect on W chromosome gene-expression patterns, with a strong convergent pattern of up-regulation associated with increased female-specific selection. Many of the transcriptional changes in the female-selected breeds are the product of positive selection, suggesting that selection is an important force in shaping the evolution of gene expression on the W chromosome, a finding consistent with both the importance of the W chromosome in female fertility and the haploid nature of the W. Taken together, these data provide evidence for the importance of the sex-limited chromosome in a female heterogametic species and show that sex-specific selection can act to preserve sex-limited chromosomes from degrading forces.
