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  3. Dolly was no ordinary lamb. She was cloned from a single mammary cell of an

Dolly was no ordinary lamb. She was cloned from a single mammary cell of an

游客2023-12-22  52
问题     Dolly was no ordinary lamb. She was cloned from a single mammary cell of an adult ewe, overturning long-held scientific dogma that had declared such a thing biologically impossible. Her birth set off a race in laboratories around the world to duplicate the breakthrough and raised the specter of human cloning.   
    A decade later, scientists are starting to come to grips with just how different Dolly was. Dozens of animals have been cloned since that first little lamb and it’s becoming increasingly clear that they are all, in one way or another, defective.
    It’s tempting to think of clones as perfect carbon copies of the original—down to every hair and quirk of temperament. It turns out, though, that there are various degrees of genetic replication. Not only are clones separated from the original template by time—in Dolly’s case, six years—but they are also the product of an unnatural molecular mechanism that turns out not to be very good at making identical copies.
    But scientists see a role for cloning in treating human diseases—and perhaps someday conquering some of man’s most intractable conditions. It may be another 10 years or more before the approach yields anything safe and reliable enough to be used in real patients, and there is no guarantee that it will ever be successful. But nobody thought Dolly was possible until she made history that warm July night 10 years ago.
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答案     多利羊绝不是普通的羊羔，它由成年绵羊的体细胞克隆而成。科学界长期认为克隆是生物学领域不可能创造的奇迹，多利羊的诞生颠覆了这一科学教条。它的出生使全世界各大实验室纷纷加入克隆的竞赛，希望再现这项科学上的突破，它的出生也使克隆人的可怕前景展现在我们面前。
    十年以后，科学家开始发现多利羊与普通羊的许多不同之处。克隆羊诞生后，数十种动物都复制出来，但是有越来越多的情况表明，这些克隆动物存在着这样或那样的缺陷。
    我们希望克隆出的个体是母体的翻版，小到每一根毛发，大到每一点脾性的怪癖，都毫无二致。然而，事实表明，尽管基因在不同程度上得到了复制，却仍然存在不少缺陷。首先，克隆的个体和母体在时间上有断层，多利羊和它的母体羊就相差六岁，同时，克隆个体仍然是人工分子机制的产物，这样的机制似乎还不擅长进行完全复制。
    科学家认为克隆在治疗人类疾病方面将起到一定作用，也许终有一天能够克服一些最难以寻找病因的人类疾病。要达到安全可靠的结果尚需时日，需要十年，也许更长，成功与否也未能完全确定。但是有谁想过多利羊能够出世呢?而在十年前那个温暖的六月夜晚，多利羊创造了历史。
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