Dolly the cloned sheep is no more. The Roslin Institute announced last week that she had been put down after a veterinary examination showed that she had a progressive lung disease. Her final resting place will be in Edinburgh - her body is to be preserved for the National Museum of Scotland.
Dolly was born in 1996 after being cloned from a mammary cell of a six-year old ewe - she was the world's first mammal to be cloned from an adult cell. Sheep normally have a lifespan of about 11 or 12 years but reports have previously suggested that Dolly was old before her time. She had shorter than normal telomeres - pieces of DNA that shorten as cells divide. These act as a kind of cellular clock, marking the number of times a cell has replicated its genetic material. Each time a cell divides to make two new cells, its telomeres get shorter, until eventually it stops multiplying altogether.
In 2002, she was also found to have a form of arthritis more common in older sheep than herself, and the lung disease she was recently diagnosed with becomes more common with age. Her health problems have inevitably raised questions about whether cloning technology causes premature ageing.
Dr Harry Griffin, from the Roslin Institute, said that any 'significant findings' would be reported after a full post mortem analysis has been conducted. Professor Richard Gardner, chair of the Royal Society stem cell and therapeutic cloning working group, said the results of the post mortem on Dolly will be necessary 'in order to assess whether her relatively premature death was in any way connected with the fact that she was a clone. If there is a link, it will provide further evidence of the dangers inherent in reproductive cloning and the irresponsibility of anybody who is trying to extend such work to humans'.