It's now 20 years since the birth of Dolly the sheep,the first mammal to be cloned. This groundbreaking scientific achievement was accompanied by warnings that Dolly might age prematurely because she had been cloned from adult sheep cells, whose "biological clock" had not been reset. Fears were heightened in 2001 when Dolly was diagnosed with osteoarthritis at five years of age (she died two years later). This was heralded as evidence of premature ageing, or although the condition is actually very poorly described in sheep.
Source: phys.org