In his paper “Dolly: The Age of Biological Control”, Ian Wilmut suggests one interesting use for cloning technology. In that paper Wilmut basically opposes what we normally think of as reproductive cloning. (In a recent paper with Glenn McGee he has slightly softened his attitude.) But he thinks the following procedure, which as far as I can tell would be illegal under current anti-cloning legislation, would be entirely appropriate if provably safe. I agree with Wilmut, and I think there’s a very strong argument for amending the legislation to ensure this procedure is permissible.

But there is one way nuclear transfer technology might be used in procreation that I do find attractive. This is its use to replace the mitochondrial DNA in an egg. Mitochondria are the small bodies in each of our cells which supply energy. They contain DNA, which is subject to error (mutation) leading to diseases in just the same way that chromosomal mutation may cause disease. However, in the case of mitochondria we inherit those only from our mothers. A woman suffering from mitochondrial disease knows that her children will inherit the same condition. In principle, there is no reason why the embryo nucleus could not be removed from the defective egg and be placed in a recipient egg cell, itself enucleated. The recipient egg would be provided by a woman known not to have similar damage to her mitochondria, with her full informed consent. The resulting child would be exactly as it would have developed, except that it would not suffer the disease associated with mitochondria. The catch with this is that it would be possible to make multiple copies of the embryo—you might start with a thirty-cell embryo and end up with six fertilized eggs. Done thoughtfully, however, this method of nuclear transfer could provide a way to treat currently untreatable mitochondrially carried diseases.

If you think 30 cell embryos are worthy of legal defence, then I guess you shouldn’t like this idea. But that is very much a minority position, and I can’t see why anyone else should oppose Wilmut’s proposal, provided it is safe.