1. Start with two eggs – one from a mum-to-be with diseased mitochondria, one from a donor with healthy mitochondria. Remove nuclear DNA from both eggs.
2. Transfer nuclear DNA from the mother’s egg into the donor egg, which contains only healthy mitochondria but no nuclear DNA. Discard remainder of mother’s egg.
3. Fertilise the complete egg – now containing the mum’s nuclear DNA – with the father’s sperm. Allow to develop into an embryo.
4. Implant the embryo, now containing donor mitochondria, and DNA from both the mum and the dad – three parents in total – into the mother’s womb.
1. Start with two egg cells – one from a mum-to-be with diseased mitochondria, one from a donor with healthy mitochondria. Fertilise both with the dad’s sperm.
2. Remove the pronuclei – the nuclei of the egg and the sperm, which have not yet mixed together – from both eggs. Discard the rest of the mother’s egg. Discard donor’s pronuclei.
3. Inject the pronuclei of the mother and the father into the donor’s egg, which contains healthy mitochondria.
4. Implant embryo, which contains mitochondria from the donor, and DNA from both the mother and the father – three parents in total – into the mother’s womb.
mtDNA = mitochondrial DNA