Three for all

Pearlman examines the ethics, as well as safey and efficacy of assisted reproduction. Mitochondrial replacement techniques (MRTs) are the latest example. The suite of procedures use DNA from three people to make a baby: the nucleus of one woman's egg, the mitochondria of another woman's egg and a sperm. MRT can be used in the UK for women who risk passing on mitochondrial disease. But discussion has now turned to a specific application: allowing same-sex female couples to have genetically related children. In the absence of other means to share genes between two eggs, and despite the low level of genetic relatedness between mitochondrial donor and child (about 0.2 per cent), MRTs seem an obvious way to fulfil this need