英語六級選詞填空練習(xí)題

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英語六級選詞填空練習(xí)題

　　It was 10 years ago, on a warm July night, that a newborn lamb took her first breath in a small shed

英語六級選詞填空練習(xí)題

　　in Scotland. From the outside, she looked no different from thousands of other sheep born on（36）farms. But Dolly, as the world soon came to realize, was no（ 37）lamb. She was cloned from a singlecell of an adult female sheep,（38）long-held scientific dogma that had declared such a thingbiologically impossible.

　　A decade later, scientists are starting to come to grips with just how different Dolly was. Dozens ofanimals have been cloned since that first lamb_mice, cats, cows and, most recently, a dog--and it'sbecoming （39）clear that they are all, in one way or another, defective.ctive.

　　It's（40）to think of clones as perfect carbon copies of the original. It turns out, though, tha!there are various degrees of genetic（41）. That may come as a shock to people who have paidthousands of dollars to clone a pet cat only to discover that the baby cat looks and behaves（42）liketheir beloved pet--with a different-color coat of fur, perhaps, or a（43）different attitude toward itshuman hosts.

　　And these are just the obvious differences. Not only are clones（44）from the original template(模板) by time, but they are also the product of an unnatural molecular mechanism that turns out not to bevery good at making（45）copies. In fact, the process can embed small flaws in the genes of clonesthat scientists are onlv now discovering．

　　A．a(chǎn)bstract

　　B．completel

　　C．deserted

　　D．duplication

　　E．everything

　　F．identical

　　G．increasingly

　　H．miniature

　　I．Nothing

　　J．ordinary

　　K．overturning

　　L．separated