This same technique was later used to create Dolly the sheep, and their experiment was the first time a successful nuclear transplantation had been accomplished in higher animals.

But it does mean that, at present, cloning of mammals is not possible by nuclear transplantation.

While the nuclear transplantation and other experiments make it clear that all nuclei contain the same genetic information, there are exceptions.

Dr. Bert Vogelstein of Johns Hopkins University proposed "nuclear transplantation."

The approved term for the technique, the university informed reporters, was "nuclear transplantation (or transferral) to produce human pluripotent stem cell lines."

Their experiment was the first successful nuclear transplantation performed in metazoans.

"Insignificant as they appeared, the specks were precious because they were, to our knowledge, the first human embryos produced by the technique of nuclear transplantation, otherwise known as cloning."

He is best known for his pioneering research in nuclear transplantation, and cloning.

Porter also contributed to the development of other experimental methods for cell culture and nuclear transplantation.

John Gurdon used nuclear transplantation to clone an African Clawed Frog; first cloning of a vertebrate using a nucleus from a fully differentiated adult cell.