Sir John Gurdon: I think I should explain that when I was doing this work, we did not know whether all the cells of the body have the same genes.  Genes are important in deciding how our cells function.  And it was unclear — it has been for thousands of years — whether cells in the body all have the same genes or whether, for example, the brain cells would have different genes from skin cells.  One idea was that the reason brain cells are different from skin is because their genes are different.  Actually, it turns out that they all have the same genes.  This was not known, and I was put onto the project of trying to do experiments to find out whether different kinds of cells all have the same genes or they don’t.  It’s a fairly clear question.