In recent US research, laboratory mice bred to have shorter telomeres went prematurely grey, got cancer more often and died early. The cloning technology requires cells to be cultured in the laboratory for a period of time, which further reduces the length of the telomeres. Dr Coleman says the research will need to be followed up on many more cloned animals. But from what they know already, he says he would not recommend cloning clones because this would only amplify any problems that might exist. The research also has important implications for the new stem cell technologies, now exciting huge interest.
Scientists believe they can ally cloning and stem cells to create perfect-match transplant tissue.
They envisage, for example, leukaemia victims being able to provide their own bone marrow transplants. But the cloning process involved in creating these replacement cells would have an effect on their telomeres. If you put these cells back into a human, you would be asking yourself how long they would last. He believes one thing is certain - Dolly and all the other clones now being created around the world will tell us a lot more about the lifecycle of cells and the ageing process. The BBC is not responsible for the content of external internet sites.