First cloned sheep Dolly dies at 6
LONDON, England -- Dolly, the world's first cloned sheep, has been euthanized after being diagnosed with progressive lung disease, the Roslin Institute has said.
The decision was taken to end her life at the age of 6 after a veterinary examination confirmed the lung disease, a statement from the institute said.
"Sheep can live to 11 or 12 years of age and lung infections are common in older sheep, particularly those housed inside," said Dr. Harry Griffin, head of the institute.
"A full post-mortem is being conducted and we will report any significant findings."
Dolly, a Finn Dorset named after the country-western singer Dolly Parton, made headlines worldwide in 1996 when she became the first mammal to be cloned with DNA taken from an adult cell.
A team led by professor Ian Wilmut of the Edinburgh-based Roslin Institute took Dolly's DNA from a ewe's udder.
Her birth was heralded as one of the most significant scientific breakthroughs of the 1990s, but it also triggered furious debate about the ethics of cloning -- a row which has deepened with claims of human cloning.
In January 2002, Dolly was diagnosed as having arthritis, a condition usually expected in older animals.
It was not clear whether the cloning process led to the arthritis, but research in 1999 suggested that Dolly might be susceptible to premature ageing -- a possibility raised after a study of her genetics.
A team from the Edinburgh-based biotech company PPL Therapeutics examined structures in Dolly's cells called telomeres. The team found that the structures were slightly shorter than would be expected in a sheep of her age which was born normally.
"The real issue is what Dolly died from, and whether it was linked to premature ageing. She was not old by sheep standards to have been put down," human cloning expert Dr. Patrick Dixon told the UK Press Association.
"The greatest worry many scientists have is that human clones -- even if they don't have monstrous abnormalities in the womb -- will need hip replacements in their teenage years and perhaps develop senile dementia by their 20th birthday.
"This is why Dolly's health is so crucial and why scientists around the world will be waiting for the results of a post-mortem examination on her."
Wilmut said last year that Dolly's arthritis showed their cloning techniques were "inefficient" and needed more work. Still, he said Dolly could live to be 10 years old.
Under UK law, therapeutic cloning -- the duplication of human embryos for research aimed at developing new stem cell treatments -- is allowed, but the cloning of humans is not.
Dolly's body has been promised to the National Museum of Scotland and will be put on display in Edinburgh in due course, a spokesman for the Roslin Institute told PA.