Oh, No! Dolly the Sheep is Getting Wrinkly!

Research published in Thursday's issue of the journal Nature suggests that the cloned ewe named Dolly could be -- as an observer once joked -- a sheep in lamb's clothing. The three-year-old Finn Dorset ewe, it turns out, may be susceptible to premature aging. Researchers have determined that chromosome tips, known as telomeres, which regulate the lifespan of cells by preventing their genetic code from fraying, are shorter than expected in Dolly. Researchers are not sure whether the "older DNA" is the result of the age of the animal from which Dolly was cloned or the result of the amount of time the Dolly embryo spent in culture before being implanted.

"This is the first major sign that there is no such thing as a perfect clone," says TIME senior science writer Jeffrey Kluger. "There has always been concern that when you copy, what you get is no better, and maybe a little worse, than the original, as when you copy a document." These findings raise questions not only about what you get with the first copy, but also what you might get with copies of copies. There is no indication yet that Dolly will die prematurely -- the shortened telomeres may have lessened her cells' genetically-programmed maximum lifespan; however, this may still be longer than the 13 years a sheep usually lives. On the other hand, could the older cells be more susceptible to disease? Researchers are eager to answer these questions.