ALAS poor Dolly, we knew her well. Last week, the most famous sheep in history was painlessly put down, aged six and a half, after she had developed an incurable lung disease.
鈥淲hile we are very sad at losing her, it鈥檚 an experiment that turned upside down our previous view of developmental biology,鈥� says Ian Wilmut, the researcher who created Dolly in 1996 at the Roslin Institute in Edinburgh.
A post-mortem revealed that Dolly, who survived only half her expected lifespan, had a lung tumour triggered by a virus. Wilmut thinks her premature death was unrelated to the cloning process by which she was created from the udder cell of a six-year-old ewe (New Scientist, 1 March 1997, p 4). A sheep housed close to Dolly died two years earlier from the same condition and may have infected her. 鈥淲e have been aware this was a risk for Dolly,鈥� Wilmut says, adding that sheep infections spread more easily indoors.
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Wilmut says that Dolly might still have had to be put down at a young age because of the arthritis she developed two years ago. But he doubts whether her ailments arose because the cell from which Dolly hailed had undergone six years of wear and tear with its original owner.
鈥淭he only obvious abnormalities from the post-mortem were the arthritis and the tumour,鈥� says Wilmut. More clues may emerge in a few weeks鈥� time following analyses of her tissues, cells and DNA by Susan Rhind, a veterinary pathologist at the University of Edinburgh.
Earlier this week, Wilmut held a 鈥渨ake鈥� at Roslin to 鈥渘ote Dolly鈥檚 passing, to signify the importance of the experiment and to say thanks to the people who looked after her鈥�. Dolly is survived by six healthy offspring, all conceived normally.
Wilmut confirmed that there are no plans to re-clone Dolly. Instead, the world鈥檚 first ovine megastar will be stuffed and displayed at the National Museum of Scotland.