John Gurdon quotes:

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.

For my part, I have worked all my life with eggs and embryos of frogs. Compared to other small animals, these have figured prominently in the world of literature.

It is particularly pleasing to see how purely basic research, originally aimed at testing the genetic identity of different cell types in the body, has turned out to have clear human health prospects.

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.

My first attempts to transplant nuclei in Xenopus were completely unsuccessful, because the Xenopus egg, unlike those of other amphibians, is surrounded by an extremely elastic membrane and jelly layer that make penetration by a micropipette impossible.

The earliest example known to me of replaced body parts is exemplified by a Mayan skull dating back to 1400 BC. In this skull, false teeth made of stone had been implanted.

I take the view that anything you can do to relieve suffering or improve human health will usually be widely accepted by the public - that is to say, if cloning actually turned out to be solving some problems and was useful to people, I think it would be accepted.

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.

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

As with most animal eggs, the early events of amphibian development are largely independent of the environment, and the processes leading to cell differentiation must involve a redistribution and interaction of constituents already present in the fertilized egg.

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.

I remember that, at an early age, I spent many months making a three-masted sailing boat with rigging in a half-walnut shell.

I must have been born with a strong attraction toward, and possibly even an aptitude for, doing things on a small scale.

Nuclear transplantation is a technique that has enormously facilitated the analysis of these interactions between nucleus and cytoplasm.

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.

The first point to remember is that attempts to clone mice have actually been very unsuccessful for at least a decade. Sheep have been successful. So one asks, 'Where do humans lie?' Most people think they are somewhere between the two, but at least there's a reasonable chance they might be clone-able.

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.

I get into lab early and leave a bit early, too. So I like to have an hour or two before everybody comes in.

The aim of a nuclear-transplant experiment is to insert the nucleus of a specialized cell into an unfertilized egg whose nucleus has been removed.

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

I myself have been a major beneficiary of the view that no animal will more repay treatment that is kind and fair.

There's a danger of some of the best people saying, 'I don't want a career in science.'

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.

The importance of the egg's non-nuclear material - the cytoplasm - in early development is apparent in the consistent relation that is seen to exist between certain regions in the cytoplasm of a fertilized egg and certain kinds or directions of cell differentiation.

I have this rather amazing report which, roughly speaking, says I was the worst student the biology master had ever taught.

I think that I cannot immediately see the route by which we should really understand memory and the workings of the brain.

I wondered whether the nuclear transfer techniques could be used to introduce purified macro-molecules into an egg, and hence into embryonic cells.

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.

If you explain to a patient what can be done and what might be the downsides, let the patient choose; don't have ethicists, priests, or doctors say you may or may not have replacement cells.