Ever since Dolly the sheep was famously cloned more than two years ago, scientists have been troubled by a nagging question: Will an infant animal that is a genetic photocopy of an adult live a full life, or will the advanced years of its "parent" make it older too? Last week the first answers arrived, and the news was not good. Some clones may indeed be growing old before their time, according to a study in the journal Nature.
The problem appears to involve telomeres, cufflike bands at the ends of chromosomes that cap the strands like the plastic sleeves at...
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