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  3. Our brains could be hard-wired to be male or female long before we begin to grow testes(丸)or ovaries(卵巢)in the womb. This discov

Our brains could be hard-wired to be male or female long before we begin to grow testes(丸)or ovaries(卵巢)in the womb. This discov

admin2014-03-15  80
问题    Our brains could be hard-wired to be male or female long before we begin to grow testes(丸)or ovaries(卵巢)in the womb. This discovery might explain why some people feel trapped in a body that’s the wrong sex, and could also lead to tests that reveal the true "brain sex" of babies born with ambiguous genitalia(生殖器).
   Till now, the orthodoxy among developmental biologists has been that embryos develop ovaries and become female unless a gene called SRY on the Y chromosome is switched on. If this gene is active, it makes testes develop instead. This switch is seen as the key event in determining whether a baby is a girl or a boy. Only after the gonads(性腺) form and flood the body with the appropriate hormones, the theory goes, is the sex of our minds and bodies determined.
   But in a study of mice, a team at the University of California, Los Angeles, has now found that males and females show differences in the expression of no fewer than 50 genes well before SRY switches on. "It’s the first discovery of genes differentially expressed in the brain, "says Eric Vilain, who led the UCLA team. "They may have an impact on the hard-wired development of the brain in terms of sexual differentiation independent of gonadal induction."
   Vilain is presenting details of seven of the 50 genes to the annual meeting of the American Society of Human Genetics in Baltimore this week. Three of these genes are dominant in females and four are dominant in males. The next step for Vilain and his team will be to show that the genes in question really do influence brain sexuality—and not just in mice. This is likely to be a much tougher proposition than merely showing there are differences in expression.
   But if the findings are confirmed, they could one day yield blood tests that allow doctors to establish the brain sex of babies born with genitalia that share features of both sexes. At present doctors and parents have to guess which gender to assign for surgical "correction".
According to the orthodoxy among developmental biologists, if SRY is active,______.
选项 A、the baby can either be a boy or a girl
B、the baby will surely be a girl
C、the baby will definitely come to be a boy
D、the baby will certainly develop ambiguous genitalia
答案C
解析  第2段中指出男性还是女性主要取决于SRY基因是否开启。如果不开启，结果就是女性；如果开启，SRY基因变得活跃，结果就是男性。
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