Man's best friend has joined the long list of animals that have been cloned in the laboratory but the scientists behind the world's first cloned dog have warned that the procedure is too dangerous to create carbon copies of favourite pets.
Scientists in South Korea announced yesterday that they have produced a cloned puppy, created from skin cells taken from the ear of an adult male Afghan hound.
Parts of the cells were incorporated into canine eggs cells to produce more than 1,000 cloned embryos, one of which was carried by a golden labrador acting as a surrogate mother for the cloned puppy.
Since the announcement of Dolly the sheep in 1997 scientists have cloned many different species, including mice, rats, cows, pigs, rabbits, cats, a mule, horses and a gaur - an endangered ox.
However, despite several attempts, a cloned dog has proved elusive because of the difficulty of maturing canine eggs in the artificial surroundings of a cloning laboratory.
Professor Woo-Suk Hwang of Seoul National University and his colleagues overcame the technical problems and yesterday unveiled the result of their research - an Afghan hound called Snuppy, a puppy named after Seoul National University's initials.
Snuppy was born in April and was one of two cloned dog embryos to be delivered alive. The second, born in May, died of pneumonia just three weeks after birth.
However, in total the scientists created 1,095 cloned embryos and implanted all them into the wombs of 123 canine surrogates. Yet only three pregnancies were confirmed, one of which ended in a miscarriage.
The extremely low success rate - two puppies from 123 surrogate mothers and more than 1,000 embryos - underlines the dangerous and haphazard nature of the cloning technique that scientists use to create clones of adult animals.
Professor Hwang and his colleague Professor Gerald Schatten of the University of Pittsburgh School of Medicine in Pennsylvania said that the aim of the study was to investigate the possibility of creating cloned embryos for producing stem cells rather than to develop a new way of reproducing animals or humans.
Both scientists emphasised that the research should not be seen as bringing human reproductive cloning any closer, or even making it ethical to clone favourite pets.
"We are not in the business of cloning pets. Nuclear transfer [cloning] is an extraordinary tool for scientific and medical research. It has never been about reproductive medicine or making any members of our family - even our pets," Professor Schatten said.
"Indeed the dismal success rate of 0.09 per cent reiterates that reproductive cloning is inefficient, unnatural and restricted to scientific and medical research applications," he said.
Professor Hwang, whose team also produced the first cloned human embryos and the first viable stem cells from cloned human embryos, said that cloning dogs will help scientists understand the problems of creating stem cells from cloned embryos and will not lead to the cloning of human babies.
"That is not our interest or purpose. Our goal with cloning research is to find cures for debilitating diseases and illnesses," Professor Hwang said.
"The characteristics of domestic animals oocytes [eggs] are very different from those of humans. Human cloning is unethical and should be banned over the world. Human cloning is no way the aim of our research team," he said.
Being able to clone dogs should enable scientists to better understand the genetic basis that accounts for the differences between different dog breeds and it may also lead to better veterinary treatments using stem cells.
"If canine embryonic stem cells are established, it would provide another therapeutic cloning model so that perhaps man's best friend might be among the first beneficiaries of stem-cell transplantation," Professor Hwang said.
Professor Ian Wilmut of Edinburgh University, who cloned Dolly the sheep, said that Professor Hwang seems to have successfully overcome the technical problems of cloning dogs by using a source of high-quality eggs.
"Professor Hwang and his colleagues allowed maturation to proceed in the dog before recovering eggs which had matured within the animal at the appropriate stage," Professor Wilmut said.
"There is a great need for a global ban on human reproductive cloning. Successful cloning of an increasing number of species confirms the general impression that it would be possible to clone any mammalian species, including humans, given an optimised method," he said.
Dr Freda Scott-Park, the incoming president of the British Veterinary Association, said that no one should underestimate the far-reaching consequences of cloning the first dog.
"Sadly the media interest is likely to attract pet owners keen to re-create their much loved pets although this demand is unlikely to be met until the efficiency of cloning is raised," Dr Scott-Park said.
"No one can deny that techniques that advance our understanding of diseases and their therapy are to be encouraged but cloning of animals raises many ethical and moral issues that have still to be properly debated within the profession," she said.