Part of the show Stem cells and Brain repair
Dolly the cloned sheep has developed arthritis in one of her back legs, denting public confidence in the safety of the cloning technology that brought her into being, and knocking 16% off the share price of PPL therapeutics, the company that helped to clone Dolly. Although arthritis is not uncommon in sheep, most animals don't show signs of joint problems until they are at least 10 years old, but Dolly is only 5 and a half. It's important not to jump to conclusions under these circumstances and indeed it could be that because she is such a celebrity, Dolly is under much closer scrutiny than most sheep would be, and so that her joint problems, which might normally have gone unnoticed, have come to light. But experts say that the joints involved, her hind knee and hip, are unusual places for arthritis. However, having led a relatively pampered life, Dolly is somewhat overweight, a condition known to aggravate joint disease, and she also has the rather unusual habit of standing on her hind legs to receive treats. Scientists have recently looked at 335 other cloned animals, including cows and sheep, and found no increased levels of joint diseases amongst them, suggesting that Dolly's arthritis is probably a coincidence rather than a consequence of cloning.