美国宾夕法尼亚州立大学的两位科学家研究发现：Y染色体比X染色体的演化速度快得多，这将导致Y染色体上的基因急剧丢失，照此继续，Y染色体将会完全消失，人类的传宗接代将受危胁。
这个现象由生物学副教授卡特雷纳·玛克瓦(Kateryna Makova)和美国国家科学基金会(ational Science Foundation)研究员梅利莎·威尔逊(Melissa Wilson)共同发现，研究成果发表在最新一期的《公共图书馆·遗传学》杂志上。
科学家表示，人类有23对染色体，染色体是由两条双螺旋DNA组成，而DNA又由无数的基因组成，其中只有一对染色体是性染色体，其他的称作非性染色体。研究小组通过对动物中的X和Y染色体的DNA和人的非性染色体中的DNA进行比较，发现X和Y染色体的DNA随着时间变化，与非性染色体的DNA的交换速度不同。卡特雷纳教授说：“研究表明，Y染色体在演化过程中表现出特异性，因为演化速度快，DNA区域分成两个实体，而在X染色体的DNA则与非性染色体保持相同的进化速度。”
研究小组假设：Y染色体的有些基因很重要，因此被保留了下来。科学家对X染色体和Y染色体上的基因表达和功能进行了类比。“如果它们之间的基因表达和功能是不同的，那么表明Y染色体由于存在X染色体上所不具备的基因功能而被保持了下来。”实验也证明也他们假设的正确性。虽然在Y染色体有些基因一直保存着，但跟X染色体相比，有不少基因已经消失了，而且有证据表明，保存下来的基因正在走向退化和消失。在未来的日子里，研究小组计划利用电脑对Y染色体新生成的数据进行模式追踪，以测定Y染色体的退化率，确定Y染色体的预计消失时间。他们也希望能够找到导致Y染色体退化的最重要的原因。 （生物谷Bioon.com）
生物谷推荐原始出处：
PLoS Genet 5(7): e1000568. doi:10.1371/journal.pgen.1000568
Evolution and Survival on Eutherian Sex Chromosomes
Melissa A. Wilson1,2,3, Kateryna D. Makova1,2,3*
1 Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America, 2 Center for Comparative Genomics and Bioinformatics, Pennsylvania State University, University Park, Pennsylvania, United States of America, 3 The Integrative Biosciences Program, Pennsylvania State University, University Park, Pennsylvania, United States of America
Since the two eutherian sex chromosomes diverged from an ancestral autosomal pair, the X has remained relatively gene-rich, while the Y has lost most of its genes through the accumulation of deleterious mutations in nonrecombining regions. Presently, it is unclear what is distinctive about genes that remain on the Y chromosome, when the sex chromosomes acquired their unique evolutionary rates, and whether X-Y gene divergence paralleled that of paralogs located on autosomes. To tackle these questions, here we juxtaposed the evolution of X and Y homologous genes (gametologs) in eutherian mammals with their autosomal orthologs in marsupial and monotreme mammals. We discovered that genes on the X and Y acquired distinct evolutionary rates immediately following the suppression of recombination between the two sex chromosomes. The Y-linked genes evolved at higher rates, while the X-linked genes maintained the lower evolutionary rates of the ancestral autosomal genes. These distinct rates have been maintained throughout the evolution of X and Y. Specifically, in humans, most X gametologs and, curiously, also most Y gametologs evolved under stronger purifying selection than similarly aged autosomal paralogs. Finally, after evaluating the current experimental data from the literature, we concluded that unique mRNA/protein expression patterns and functions acquired by Y (versus X) gametologs likely contributed to their retention. Our results also suggest that either the boundary between sex chromosome strata 3 and 4 should be shifted or that stratum 3 should be divided into two strata.
