Britain | Reproductive medicine

A dad and two mums

MPs vote in favour of children with three genetic parents

A new kind of threesome

EVERY year around a hundred children are born in Britain with seriously damaged mitochondria, those parts of a living cell that synthesise the chemical fuel that powers the rest of it. It is often a death sentence. Those who survive live a debilitating existence in which the tissues of their bodies—brains, muscles, nerves and the rest—are chronically short of the energy they need to function.

There is no cure. But there might be a way to help the roughly 2,500 women whose future children would be at risk. On February 3rd the House of Commons voted, by 382 to 182, to make Britain the first country in the world to permit “mitochondrial donation”, a form of in-vitro fertilisation (IVF) designed to ensure that those children can be born free of the condition.

It was a free, unwhipped vote because, despite the potential benefits, the issue is contentious. The procedure involves transplanting the nucleus from an egg cell with damaged mitochondria into another egg with healthy ones. That second egg is provided by a donor.

Mitochondria are different from other cellular components. They are the distant descendants of free-living bacteria that, in the deep evolutionary past, became symbiotic with the cells they now inhabit. As such, they contain their own tiny genomes, separate from the main human genome that resides in the nucleus. A baby created via mitochondrial donation will thus have genes from three people—its mother, its father, and the woman who donated the egg.

The amounts in question are small. Humans have about 22,000 genes. Mitochondria have 37, all of which are concerned with the nuts and bolts of low-level biochemistry. So the small slice of mitochondrial DNA from the donor should not affect things like eye colour, height or personality, which will be influenced by the child’s parents in the usual way. But since all the mitochondria in a person’s body are descended from the original few in the egg, women born via the procedure will pass the modifications to their children in turn.

The noisiest opposition came from traditionalists and the religious—a weakening lobby in a country that is becoming ever more secular, and one that in this case was divided. The Church of England supports the idea in theory, although it wants more research, and some priests have spoken out against. The Roman Catholic church is opposed, as it is to all forms of IVF; Britain’s Muslims are split. Polls suggest that a majority of the public, once informed about the procedure, are in favour.

IVF clinics will not rush to offer it. Assuming the bill clears the House of Lords, mitochondrial donation will remain illegal until October. Clinics will need a licence from the Human Fertilisation and Embryology Authority, which regulates fertility medicine, as well as specific permission to treat each couple. Any children born as a result will be followed up, to check for unforeseen complications.

Doug Turnbull, a scientist at the University of Newcastle who has led much of the research into mitochondrial donation, reckons that about 150 families a year could benefit. But he thinks that, while the technique is new and relatively untried, only a minority will go for it. Much will depend on whether the NHS agrees to pay, as it does for some but not all IVF patients. Yet the ranks of British early adopters could be swelled by couples from overseas. By the end of this year, Britain is likely to be the only place in the world where they will be able to have children who can hope to lead ordinary, healthy lives.

This article appeared in the Britain section of the print edition under the headline "A dad and two mums"

Capitalism’s unlikely heroes

From the February 7th 2015 edition

Discover stories from this section and more in the list of contents

Explore the edition

Discover more

The future of Drax, Britain’s largest power plant

From coal to wood to carbon capture and storage?

A new hate-crime law in Scotland causes widespread concern

Transgender identity is protected; biological sex is not


Britain’s kings of sourdough

The rapid rise of a firm that makes bread very slowly