美国科学60秒 SSS 2013-07-30

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　　It takes a white chromosome¹ to make a man, but that does't mean its counterpart, the x-chromosome, plays no part. In fact it has a big role in making sperm².

　　To study x evolution, experts first sequence human chromosome more accurate than it ever before. Then they compare the code to that of a mammal whose evolutionary³ lineage spit from ours about 80m yrs before, the mouse. It turns out that human and mice share 95% of their x-genes⁴, this finding was no surprise.

　　In the 1960s, biology S.O. suggests that the x-chromosome would evolve slowly and almost remain similar in most mammalia species. But something did change over evolutionary time, or rather 144 things. 144 human x-chromosome genes had no counterparts in mince⁵ and these genes seems to be constantly developing. Many of the genes remained domain⁶ in female, only become productive in tissues involved in sperms⁷ production. Clearly, the ex-chromosome exceeds its feminine responsibilities, which is excellent news for male fertility.

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