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　　中英文本

　　When you hear the word "mutation," you may thinkof something destructive, or of Marvel's X-Men. Butsome mutations—which are just differences in DNA—can be historic. Take, for example, a geneticsequence found in the vast majority of peoplefrom Tibet.

　　当你听到“突变”这个词的时候，你可能会联想到某些具有破坏性的东西，或漫威漫画公司出品的X战警。但有些突变，如基因差异，却是有历史意义的。下面就拿一组基因序列来说吧，该组基因序列存在于绝大多数的西藏居民中。

　　Millions of Tibetans spend their days at average elevations of nearly 15,000 feet—that's morethan half the height of Mount Everest. Up there, the air is thin—with 40 percent less oxygenthan at sea level. That lack of O2 would leave most Westerners struggling for breath, butTibetans seem to breathe easy.

　　数以百万计的藏族人居住在平均海拔近15,000英尺的地方——这可是半个珠穆朗玛峰的高度。那儿，空气稀薄——氧含量比水平面低40%。由于缺乏氧气，大多数来到此地的西方人都会感到呼吸困难。但藏族人却不会。

　　To find out how these highlanders cope, researchers compared the DNA of 90 Tibetans to thatof people who are not altitude adapted. And they discovered a single change that preventsTibetans' blood from becoming dangerously clogged with red blood cells—a response that canbe deadly for non-native mountaineers. The finding is described in the journal Nature Genetics.

　　为找出其中原因，研究人员将90名藏族居民的DNA与那些不适合在当地居住的人的DNA进行比较。他们发现：藏族居民DNA里存在一个突变，该突变能防止藏族居民的血液过分充满血细胞——该反应对非当地居民的登山者来说是致命的。该项研究发表在《自然遗传》杂志上。

　　This mutation appears to have originated just 8,000 years ago. But it's so advantageous thattoday nearly 90 percent of Tibetans have it. While it's virtually absent in even closely relatedlowland neighbors.

　　该突变起源于8,000年前。如今，90%的藏族居民都有，这对他们来说真是太有利了。但那些居住在低地的、甚至与高地居民有密切血缘关系的邻居却几乎没有。

　　The finding demonstrates that a really useful mutation will always rise to the top.

　　该研究结果表明有利的突变总是能备受瞩目。

　　词语解释

　　1.Mount Everest珠穆朗玛峰

　　Birds fly over Mount Everest at altitudes where theair is so thin humans can’t function, and no oneknows how they do it.

　　鸟可以在珠穆朗玛峰上空飞行，但山上空气太稀薄人类无法呼吸，没有人知道它们是怎么做到的。

　　2.sea level 海平面

　　The Turban Basin in Xinjiang is the world's lowest-lying basin, the lowest point being 154metres below sea level.

　　中国新疆的吐鲁番盆地是世界最低的盆地。 盆地最低点在海平面以下154米。

　　3.clog with阻塞

　　Some electric clippers are unsuitable for the Bedlington coat, mainly because they clog with hairtoo easily.

　　一些电剪并不适合贝林登梗毛，这主要是因为他们太容易被毛堵住了。

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