Why did Dolly die?

Answer 1

Referring to Dolly the Sheep:

On February 14 , 2003, Dolly was euthanised because of a progressive lung disease. A Finn Dorset such as Dolly has a life expectancy of around 11 to 12 years, but Dolly lived to be only six years of age. A post-mortem examination showed she had a form of lung cancer called Jaagsiekte that is a fairly common disease of sheep and is caused by the retrovirus JSRV.

Roslin scientists stated that they did not think there was a connection with Dolly's being a clone, and that other sheep in the same flock had died of the same disease. Such lung diseases are a particular danger for sheep kept indoors, and Dolly had to sleep inside for security reasons.

However, some have speculated that a contributing factor to Dolly's death was that she could have been born with a genetic age of six years, the same age as the sheep from which she was cloned. One basis for this idea was the finding that Dolly's telomeres were short, which typically is a result of the aging process. However, the Roslin Institute have stated that intensive health screening did not reveal any abnormalities in Dolly that could have come from advanced aging.