Dolly the sheep, the first mammal to be cloned from an adult cell, was put down on Friday afternoon, after developing a progressive lung disease.



Dolly’s birth six-and-a-half years’ ago caused a sensation around the world. But as many sheep live to twice this age, her death will refuel the intense debate over the health and life expectancy of cloned animals.



The type of lung disease Dolly developed is most common in older sheep. And in January 2002, it was revealed that Dolly had developed arthritis prematurely. She was cloned using a cell taken from a healthy six-year-old sheep, and was born on 5 July 1996 at the Roslin Institute, Edinburgh, Scotland.
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