London: Dolly, the sheep, became a scientific sensation when her birth was announced in 1996.
Now, 14 years on, the scientist, who cloned Dolly, has claimed to have created four more sheep who are the exact genetic duplicates of Dolly, the world`s first mammal to be cloned from an adult somatic cell.
The quads, which have been nicknamed "the Dollies", are exact genetic copies of their predecessor who was put down seven years back only to end her suffering from advanced lung disease and arthritis, a newspaper reported.
Though critics have warned the technology brought with it a high risk of miscarriage -- and for those creatures which did survive, ill-health and premature death, Professor Keith Campbell said that the latest experiments were partly carried out to check if improvements to the technique cut the risk of problems in and out of the womb.
Named after country and western singer Dolly Parton, Dolly was created from a cell taken from a mammary gland.
The rest of the sample of tissue was kept in a freezer since, till it was defrosted to make the Dollies. This means the quads are genetically identical to each other, as well as to Dolly, and to the ewe that donated the udder tissue.
Prof Campbell, who keeps the Dollies as pets on land at Nottingham University, was quoted as saying, "Dolly is alive and well. Genetically these are Dolly."
The cloning of Dolly was a long and tortuous process. In all, 277 eggs were used and only one lamb – Dolly -- survived. And, this time, only five embryos were needed to produce each one of the Dollies.
Prof Campbell said the health of the clones was being closely watched. He added: "They have got the life of Reilly-- they potter around and get fed. We are not doing anything to them, they have no health concerns and they show none of the signs of developing the arthritis that Dolly had."
The professor, who plans to publish details about the Dollies in a scientific journal, said improvements in the technology raised the odds of clones being born alive and healthy but admitted the method was still not perfect.
The Dollies were born three-and-a-half years ago but their existence became public when Prof Campbell mentioned them during a lecture at a recent European Parliament debate on cloning and animal welfare.
He said he had not tried to hide their existence and had spoken of the animals to other scientists.
However, animal welfare campaigners say that cloned animals and their surrogate mothers still suffer immensely.
Peter Stevenson of Compassion in World Farming, said, "Cloning is a welfare disaster."