许多年以后男人将会消失?这是前段时间科学界发现决定男性特征的Y染色体上的基因数目在不断减少后出现的一种极端推论,英国研究人员就此表示,他们进行的一项最新研究表明Y染色体不会消失。
Y染色体是男性所独有的、决定男性特征的染色体。之前有研究发现,Y染色体上的基因数目在不断减少,按此速度推算在约1000万年后Y染色体将完全消失,有人因此做出了男人将随之消失的推论。
英国伦敦大学学院等机构研究人员在新一期美国《国家科学院学报》PNAS上报告说,这种极端推论是站不住脚的,对鸡的W染色体的分析就可以说明这一点。在鸡的遗传物质中,存在一种W染色体,它是母鸡所独有的,其作用与人类男性的Y染色体大致相当。研究人员调查了一些不同种类的鸡的遗传进化的情况,结果发现,在斗鸡等长期重视雄性特征的鸡中,雌斗鸡W染色体的确出现了退化;但是在另一些蛋鸡中,W染色体的功能却得到了加强。与下蛋相联系的是繁殖能力,而繁殖能力对一个物种来说是至关重要的,正是这个进化上的大前提确保了母鸡W染色体的持续存在甚至加强。
进行研究的朱迪思·曼克教授说,男性Y染色体的情况也差不多,虽然Y染色体上的基因在过去不断减少,但剩下的部分在生育中发挥着非常重要的作用,从长期来看Y染色体应该不会消失。(生物谷Bioon.com)
doi:10.1073/pnas.1202721109
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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.