自从第一只羊被克隆以来，已经有几十种动物被克隆了，包括老鼠、猫、牛和最近的一只狗；而且越来越明显的是，这些动物都有这样或那样的缺陷。
Dozens of animals have been cloned since that first lamb—mice, cats, cows and, most recently, a dog—and it's becoming increasingly clear that they are all, in one way or another, defective.
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