A cell, with the nucleus containing the bulk of genetic material in the centre and the mitochondria shown in green, and the method for conventional IVF, which has been adapted for the three-parent process © Eraxion (left) © ktsimage (right)
In June, Britain’s Chief Medical Officer gave a cautious go ahead for work on three-parent fertility treatments. The intention is to use genetic material from the two “biological” parents, and one other woman, to lessen the chances of the child inheriting certain disorders. The prospect of the United Kingdom becoming the first country to allow this has drawn strong opposition from religious and ethics groups. Some see it as “cross[ing] the line that will eventually lead to a eugenic designer baby market,” as David King, Director of campaign group Human Genetics Alert, put it. But some scientists also think that those in favour of the technique have downplayed the uncertainties.
Three-parent in vitro fertilisation works by combining the ova of two women to prevent children from inheriting faulty genes from the “principal” mother. The second woman, or “third parent,” donates only a small number of genes to correct potentially faulty ones, while the rest of the principal mother’s genetic material remains intact. This could prevent around 50 genetic diseases from being passed on, including muscular dystrophy and Parkinson’s, while, researchers claim, having no other impact on the child.
But this may not be the case. There is reason to think that including genetic material from a third parent would alter the child. There is the risk that parents might one day submit to a treatment that not only removes the chance of a child inheriting a certain disorder, but also changes its nature. The possibility is that, despite what has been claimed, “three-parent babies” would be precisely that, with a genetic make up derived from all three adults.
The piece of genetic material upon which the treatment depends are mitochondria. Almost all of an individual’s DNA and genes are contained in the “nuclear genome” that sits at the centre of our cells. But there are 37 genes—little more than 0.1 per cent of the total—that are located separately in mitochondria. These small units are located inside human cells, separate from the bulk of the genetic material, and are sometimes described as…