The innocents from the Roslin Institute near Edinburgh, who announced on 7th March that they had produced two identical Welsh mountain sheep, should not have been surprised that they triggered off yet another bout of agitation about research in genetics and embryology. Most anxiety in this field has recently centred on the use of pigs’ hearts as transplants for human patients. It is a long time since there was a fuss about what is called “cloning,” or the artificial production of individuals which are carbon copies of each other. As the seasons come and go, cloning was no doubt due for its turn again.

Even so, the hyperbole of the past few weeks has splendidly outdone science fiction. References to Brave New World have been routine (in The Times, Roger Scruton cleverly used it both to make his point and put down Aldous Huxley’s novel). The reaction has been that, now that they have done it with sheep, it is only a matter of time before they can do it with people. And then it will only be a matter of time before the rich and powerful find embryologists and physicians prepared to break the law in the interests of their genetic succession.

The people at the Roslin Institute must be wishing that it were that simple. Their purpose (they make no bones about it in their published paper) is to find a vehicle for the rapid introduction of altered genes into farm breeding stock. Given the seasonality of sheep (this is the lambing season), conventional techniques allow only the slow spread of an advantageous gene through a flock.

The extent to which the Roslin group has solved this problem is far from clear. The crux of what they have done is to extract from a nineday-old sheep embryo the tissues destined to become germ cells (the progenitors of ova and sperm); to induce cells from those tissues to multiply in the laboratory; and to show that when cells of that kind are fused with mature sheep oocytes from which the chromosomes have been removed, the result is a cell which functions as if it were a newly fertilised sheep ovum.

In other words, the fake fertilised ovum can be put into a sheep uterus (at the right season) in the expectation that it will grow to term, becoming a lamb after six months. There were five successful pregnancies…

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