Fat mice cause more cloning concern

A report published in Nature Medicine last week has cast more doubt on the safety of cloning. Scientists from the University of Cincinnati, US, say that some cloned mice became obese, even though they were fed normally and were active.

Dr Randall Sakai, leader of the research team said that the mice appeared normal in every other way. The scientists first became interested when it was reported that a team of scientists cloning mice in Hawaii had cloned a batch that grew to be obese.

Dr Sakai and his team examined nine of the mice and found that they carried excess body fat and produced higher levels of insulin and leptin, a hormone produced by fat cells, than other mice. However, when those mice were bred, their offspring did not become obese, showing that it was not a genetic trait and suggesting that the obesity may have been in some way caused by the cloning process.

The report comes only a short time after it was shown that cloned mice had a tendency to die young. The scientists said that  these results show that it would be dangerous to begin to clone humans. Ian Wilmut, the scientist who cloned Dolly the sheep, said in a commentary published alongside the report that 'cloning by the present methods is a lottery. Several coins are thrown and must all come up as heads if life is to be normal'.