Babies to be made from two women and one man

The UK House of Commons has voted in favour of a controversial technique that allows IVF babies to be created with biological material from three different people.

If the regulations are approved by the House of Lords, the UK will become the first country in the world to permit the use of mitochondrial DNA transfer techniques to stop genetic diseases being passed from mother to child.

MPs were allowed a conscience vote on the issue, with both the Labour and Conservative front benches agreeing the technique was a significant scientific advance and not a form genetic modification.

It is hoped the technique will assist the small number of children born each year with faults in their mitochondrial DNA. Mitochondrial diseases are incurable, often strike in childhood and prove fatal before adulthood. They include Barth syndrome, Leigh’s disease and progressive infantile poliodystrophy. Other conditions linked to faulty mitochondria are more common and include diabetes, epilepsy, Parkinson’s disease, failing eyesight and deafness.

Everyone has mitochondria in their cells, but only mothers pass on mitochondrial genes. Mitochondria have their own set of 37 genes, which are separate from the 20,000 or so genes on a human’s 23 pairs of chromosomes found in a cell nucleus. In mitochondrial DNA transfer, these 20,000 genes will still come from the child’s father and mother. The donor will only contribute their mitochondrial DNA.

Critics of the technique say the procedure should not take place until mitochondria are better understood (this is the Church of England’s position, although it is not opposed to the technique in principle). A concern is that the technique will pass on genetic changes from one generation to the next and could adversely affect children not yet born.

There are two ways mitochondria can be transferred.

Maternal spindle transfer

In this procedure doctors use IVF techniques to harvest eggs from the mother. The nucleus from a mother’s egg is then transferred into a donor egg from which the nucleus has been removed. The father’s sperm is then used to fertilise this egg.

Pronuclear transfer

With this technique both the mother and donor’s eggs are fertilised with the father’s sperm. The parents’ chromosomes in the nucleus of the mother’s fertilised egg are inserted into the donor’s egg, from which the nucleus has been removed. This egg is then ready to be implanted into the mother. The Catholic Church objects to this procedure because fertilised eggs are destroyed. Catholic ethicists also have a more general concern about the consequences for natural parenthood.