Scientists say they have begun to crack the genetic code that helps determine when a girl becomes a woman.

A UK-led team located two genes on chromosomes six and nine that appear to strongly influence the age at which menstruation starts.

The Nature Genetics study also provides a clue for why girls who are shorter and fatter tend to get their periods months earlier than classmates.

The genes sit right next to DNA controlling height and weight.

A second paper, published in the same journal, also concludes that one of the two genes highlighted by the first study plays a key role in the timing of puberty in both girls and boys.

Reproductive lifespan is closely linked to the risk of developing conditions such as heart disease, breast cancer and osteoporosis.

It is thought that the female sex hormone oestrogen - produced at higher rates during a woman's reproductive life - raises the risk of these diseases.

Therefore, the earlier a woman goes through puberty, the more risk she may be at.

科学家宣称已经开始破解有助于确定女孩成年的基因密码。

一个由英国领导的科研小组确定了染色体中编号为六号和九号的两条基因似乎强有力地影响了女性月经开始的年龄。

《自然遗传学》的研究也提供了一条线索，那就是矮胖的女孩为什么比班上的同学月经初潮早几个月。

基因与DNA一起控制身高和体重。

发表于该杂志的另一篇论文也断定，由第一项研究强调的两条基因中的一条对于女孩和男孩进入青春期的时间具有重要作用。

人的生殖期限与产生心脏病、乳腺癌和骨质疏松症的条件的危险紧密相连。

据说女性在生殖周期内分泌更多雌性激素使得她们更易于染上这些疾病。

因此，女性经历青春期越早，就会越危险。

研究者认为他们的工作不仅提高了我们对基因基础发展的了解，还会最终有助于抵御疾病。

然而，他们也认为青春期的开始也受到营养和运动等因素影响，单个基因的影响相对而言还是很小的。

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