The British scientists who cloned Dolly the sheep said Thursday they had made a major advance by cloning Polly the lamb, who carries human genes.
This means they can clone herds of identical sheep that produce human proteins or blood products for medical use.
Polly and four near-identical sisters are transgenic -- they are sheep, but they carry a human gene.
"It was what we told everybody we were going to do, but it's nice to be able to say we have done it," Ron James, managing director of PPL Therapeutics, said in a telephone interview.
PPL's scientists have cloned sheep before -- not only Dolly but nine others using other techniques. They have also created many transgenic animals.
This is the first time they have been able to combine the two technologies.
The five Polly Dorset lambs were not using the stunning technology that produced Dolly.
Dolly was the first mammal cloned from an adult cell. Polly and her virtually identical sisters were created by fusing a fibroblast cell from a fetus to an egg cell.