許多年以后男人將會消失？這是前段時間科學界發(fā)現決定男性特征的Y染色體上的基因數目在不斷減少后出現的一種極端推論,，英國研究人員就此表示,，他們進行的一項最新研究表明Y染色體不會消失。
Y染色體是男性所獨有的,、決定男性特征的染色體,。之前有研究發(fā)現，Y染色體上的基因數目在不斷減少,，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。
英國倫敦大學學院等機構研究人員在新一期美國《國家科學院學報》PNAS上報告說,，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。在雞的遺傳物質中,，存在一種W染色體,，它是母雞所獨有的，其作用與人類男性的Y染色體大致相當,。研究人員調查了一些不同種類的雞的遺傳進化的情況,，結果發(fā)現，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,。與下蛋相聯系的是繁殖能力,，而繁殖能力對一個物種來說是至關重要的，正是這個進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,。
進行研究的朱迪思·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染色體應該不會消失,。（生物谷Bioon.com）
doi:10.1073/pnas.1202721109
PMC:
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.
