However, if she is, then the resulting offspring could answer many questions about cloning, and perhaps even forestall the idea of cloning humans.
In particular, scientists at the Roslin Institute near Edinburgh are keen to know whether the offspring of a cloned animal are sterile, or if they have any other birth or growth abnormalities. It is already known that in the womb, cloned animals tend to be heavier and have more birth problems, and frequently fail to survive. Whether those problems are common to their children is as yet unknown.
Answering those questions is key to the commercial development of cloning for farm animals. If clones' offspring prove not to be viable, they would have to be recreated with each generation.
It is also important for those who would clone humans, such as Richard Seed, the Chicago physicist who shocked America this week by saying he wants to set up a chain of 20 human cloning clinics. The idea has been attacked as unethical.
It could also be impractical, depending on what happens in Edinburgh. "Dolly has been mated and we will wait for nature to take its course," said Dr Harry Griffin, the institute's assistant director. "We don't know if she is pregnant yet."
Staff at the institute said last September that Dolly would be taken to a ram early this year to determine whether she is fertile and can produce healthy lambs.
Dolly, now 18 months old, is a Finn Dorset breed. She was the first mammal cloned from the cell of another adult mammal.
Professor Graeme Bulfield, director of the institute, said that the breeding will determine whether Dolly's lambs would be affected by her own unusual conception. Her offspring would not be clones and would be genetically different from their mother, he said.
Healthy lambs would mean that the cloning process had produced a fully healthy, fertile sheep, which would be valuable knowledge for PPL Therapeutics, the Scottish biotechnology company formed to market the centre's work, Professor Bulfield said.
The institute has already proven that cloned animals can reproduce. Megan and Morag, sheep conceived through a different cloning process, have lambs of their own.
Dr Griffin said the institute was planning a centre where it could put Dolly, Megan, Morag and Polly, a cloned lamb carrying a human gene, on public display. He said it should be open by Easter.Reuse content