From the archive: Genes of clones are ‘abnormal’, 12 September, 2001

CLONED mice have hundreds of abnormal genes, explaining why so many cloned animals die at or before birth and proving it would be irresponsible to clone a human being.

The process of cloning introduces the genetic mutations, and there seems no immediate way around the problem, Rudolf Jaenisch and colleagues at the Massachusetts Institute of Technology reported. “I think this confirms suspicions that I have always had and that many others had that cloning is a very inefficient method at this point,” Mr Jaenisch said.

Even before Dolly the sheep became the first mammal to be cloned from an adult cell, in 1997 at Roslin, near Edinburgh, researchers have known that cloning is difficult. Only one of every several hundred eggs ever start dividing and of these, only a small percentage result in pregnancies.