美國賓夕法尼亞州立大學(xué)的兩位科學(xué)家研究發(fā)現(xiàn)：Y染色體比X染色體的演化速度快得多,，這將導(dǎo)致Y染色體上的基因急劇丟失,，照此繼續(xù)，Y染色體將會完全消失,，人類的傳宗接代將受危脅。
這個現(xiàn)象由生物學(xué)副教授卡特雷納·瑪克瓦(Kateryna Makova)和美國國家科學(xué)基金會(ational Science Foundation)研究員梅利莎·威爾遜(Melissa Wilson)共同發(fā)現(xiàn),，研究成果發(fā)表在最新一期的《公共圖書館·遺傳學(xué)》雜志上。
科學(xué)家表示,，人類有23對染色體，染色體是由兩條雙螺旋DNA組成,，而DNA又由無數(shù)的基因組成，其中只有一對染色體是性染色體,，其他的稱作非性染色體。研究小組通過對動物中的X和Y染色體的DNA和人的非性染色體中的DNA進(jìn)行比較,，發(fā)現(xiàn)X和Y染色體的DNA隨著時間變化，與非性染色體的DNA的交換速度不同,。卡特雷納教授說：“研究表明,，Y染色體在演化過程中表現(xiàn)出特異性，因?yàn)檠莼俣瓤?，DNA區(qū)域分成兩個實(shí)體，而在X染色體的DNA則與非性染色體保持相同的進(jìn)化速度,。”
研究小組假設(shè)：Y染色體的有些基因很重要，因此被保留了下來,?？茖W(xué)家對X染色體和Y染色體上的基因表達(dá)和功能進(jìn)行了類比,。“如果它們之間的基因表達(dá)和功能是不同的,，那么表明Y染色體由于存在X染色體上所不具備的基因功能而被保持了下來。”實(shí)驗(yàn)也證明也他們假設(shè)的正確性,。雖然在Y染色體有些基因一直保存著，但跟X染色體相比,，有不少基因已經(jīng)消失了,，而且有證據(jù)表明,，保存下來的基因正在走向退化和消失。在未來的日子里,，研究小組計(jì)劃利用電腦對Y染色體新生成的數(shù)據(jù)進(jìn)行模式追蹤，以測定Y染色體的退化率,，確定Y染色體的預(yù)計(jì)消失時間。他們也希望能夠找到導(dǎo)致Y染色體退化的最重要的原因。 （生物谷Bioon.com）
生物谷推薦原始出處：
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.
