Premature aging of Dolly, the cloned sheep, seen as an anomaly
In 2002, when Dolly the sheep, the first truly cloned mammal, died at the age of six, scientists studied her telomeres — the structure at the end of DNA strands that shorten with age — and found that Dolly’s were much shorter than they should be. Initially, scientists thought this meant clones would age prematurely, following the biological clock of the original cells. If so, it would be a terrible prospect for cloned human organs.