John Maddox explains the new science behind Dolly and why the ethical dilemmas can waitby John Maddox / April 20, 1997 / Leave a comment
The most shocking thing about the cloned sheep Dolly is not the fact of her existence or even that the British Ministry of Agriculture, Fisheries and Food has withdrawn support for the research that produced her, but that a ministry spokesman declined to comment on this bizarre decision-and got away with silence.
This is yet another galling illustration of how the British government (and Douglas Hogg’s ministry in particular) repeatedly makes a monkey of science. Of course, we all know the theory that protects ministerial secrecy: the government is elected to govern between general elections and need not explain administrative decisions to anybody. (MPs can demand facts, but are lucky to be given explanations.) On this occasion, whatever the excuse, the decision is just plain wrong.
That was brought home to me by a distinguished molecular biologist over lunch in Cambridge, Massachusetts on 28th February, when the US newspapers were still full of Dolly. “It may be the most important experiment this century,” he said. We argued the toss a little over that, but his meaning was clear. Like all good experiments, the cloning of Dolly overturns a good deal of conventional wisdom about the way that genes work in living creatures. It raises a string of questions only imprecisely asked in the past few years. And it is of potentially immense importance to medicine, whether or not it is ever possible and permissible to clone people.
We should be clear why the science of Dolly is so important. It has to do with how cells from different tissues of the body differ from each other, and why they stay different even when they divide, except perhaps when they become cancerous. Each cell has a full complement of DNA, exactly as in the single fertilised ovum from which an embryo develops. So why does a liver cell, say, always produce liver cells when it divides and not skin cells or nerve cells? The inference has been that the unwanted genes are somehow permanently switched off: in the liver only the genes essential to liver function are active in ordinary life.
How do cells get like that? Between the embryo and the newborn animal, there is an elaborate hierarchy of processes, all of them determined by the embryo’s genes. The general rule seems to be that cells of different degrees of specialisation arise progressively, until they eventually produce what are…