【英语时差8，16】男性生物钟
时间：2015-10-19 05:34:25
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（单词翻译）
Tick-tock, tick-tock. Is that your biological clock? And if it is, are you female? Most people think biological clocks are strictly1 female phenomena2, with infertility3 and the risk of certain diseases going up with a mother's age. But the biological clock is an equal opportunity timepiece--that's right, men have one too! There's a common belief that men can sire children until they die, but that women need to be relatively4 young to conceive healthy children. But the father's age affects the child's health too. Psychiatrist5 Dolores Malaspina and her team found that the risk of schizophrenia triples for babies born to fathers over 50, compared with fathers under 25. Other diseases appearing more in offspring of older fathers are achondroplasia, or dwarfism, and some prostate cancers.
Despite the
publicity6 given to women's biological clocks, medical geneticists recently have found that
sperm9 are more likely than eggs to have
genetic8 mutations. Here's why. By age 40, a man's sperm cells have divided over 600 times. That's over 600 chances for mistakes in copying
genes10. A woman's eggs, on the other hand, don't go through that process of division, so there are fewer chances for mistakes in
gene7 replication. When there is a genetic problem in an egg, though, it's often with a whole
chromosome11, instead of a single gene. Down
syndrome12, for example, occurs when there's an extra copy of chromosome 21. Most babies with older fathers, as with older mothers, are healthy. Still, biological clocks are real, and not just for women. His biological clock is ticking too!
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