“Three-parent” babies

Doctors in Newcastle have been granted the first UK licence to practise a new fertility technique that involves creating babies with DNA from three people. Mitochondrial replacement therapy (MRT) was developed to stop children inheriting incurable genetic conditions from their mothers. The mitochondria are tiny structures that power the cells, and which carry a very small set of their own genes. This DNA is always inherited from the mother and, though it has no influence over individual characteristics such as personality and appearance, mutations in it can cause serious problems – including brain damage, blindness, heart and liver disease, and seizures. The therapy – a form of IVF – involves replacing the faulty mitochondria in the mother’s egg cells with those of an unaffected donor before the egg is fertilised by the father’s sperm.