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".
The first paragraph tells us that ______.
A.whether we will be male or female is determined by the brain, not the genitalia
B.some people consider themselves to be male but are in fact female physiologically
C.our brain sex is formed long after our testes or ovaries begin to grow
D.some people feel trapped because they have ambiguous genitalia
第1题
实验部门预算绩效考评的主要内容有()。
A.制定明确、合理的财政支出绩效目标
B.建立科学、规范的绩效考评指标体系
C.部门为完成绩效目标采取的管理措施
D.对绩效目标的实现程度及效果实施考核与评价
E.运用考评结果提高预算编制,执行和管理水平
第2题
实验部门预算绩效考评的主要内容有()。
A.制定明确、合理的财政支出绩效目标
B.建立科学、规范的绩效考评指标体系
C.部门为完成绩效目标采取的管理措施
D.对绩效目标的实现程度及效果实施考核与评价
E.运用考评结果提高预算编制,执行和管理水平
第3题
财政支出绩效考评的关键是()。
A.选择合适的考评方法
B.确定合理的绩效考评指标
C.制定绩效目标
D.写好考评报告
第4题
财政支出绩效考评的关键是()。
A.制定绩效目标
B.写好考评报告
C.选择合适的考评方法
D.确定合理的绩效考评指标
第5题
财政支出绩效考评的关键是()。
A.选择合适的考评方法
B.确定合理的绩效考评指标
C.制定绩效目标
D.写好考评报告
第6题
是财政支出绩效考评的关键。
A.写好考评报告
B.制定绩效目标
C.选择合适的考评方法
D.确定合理的绩效考评指标
第9题
财政支出绩效考评的关键是()。
A.选择合适的考评方法
B.确定合理的绩效考评指标
C.制定绩效目标
D.写好考评报告
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