John Gurdon

I left my frogs, which I had grown, with my supervisor, who had moved to Geneva, and he and a technician grew them up. So by 1962, they were adults, and one could publish a paper to say that these animals, derived from nuclear transfer, really were absolutely normal. So it took a little time to get through.

If you took some famous religious leader, for example, and said it would be nice to clone them indefinitely so you have a dynasty of leaders, my own guess would be that each time the cloning takes place, they would become more and more defective, presumably mentally defective and subsequently worse.

The work I was involved in had no obvious therapeutic benefit. It was purely of scientific interest. I hope the country will continue to support basic research even though it may have no obvious practical value.

It's a very complex network of genes making products which go into the nucleus and turn on other genes. And, in fact, you find a continuing network of processes going on in a very complex way by which genes are subject to these continual adjustments, as you might say - the computer programmer deciding which genes ultimately will work.

Within six months of starting my Ph.D. work in 1956, I had already obtained feeding tadpoles derived from transplanted nuclei of embryonic cells.

As a brand new graduate student starting in October 1956, my supervisor Michail Fischberg, a lecturer in the Department of Zoology at Oxford, suggested that I should try to make somatic cell nuclear transplantation work in the South African frog Xenopus laevis.

Shinya Yamanaka's work has involved mice and human cells, and advances the prospect of providing new cells or body parts for patients.

In principle. what is done is to take the nucleus out of a cell with a very fine micro-pipette or needle and introduce it into an egg. That had been done with amphibians a long time ago, and then there was a long pause of many years before people were clever enough to make that work in the sheep.

Within one year of starting work, I had found that the nucleus of an endoderm cell from an advanced tadpole was able to yield some normal development up to the nuclear transplant tadpole stage.

Once the principle is there, that cells have the same genes, my own personal belief is that we will, in the end, understand everything about how cells actually work.