A research team in the UK is experimenting with creating three-parent embryos (by adding part of the egg of one woman to the egg of another) to prevent children inheriting a rare group of serious diseases caused by faulty mitochondria, the powerhouses in our cells.

Mitochondrial diseases affect at least 1 in 8000 people, probably more, and there are no treatments.

But the influence of mitochondrial genes extends far further: different variants can affect our energy, athleticism, health, aging, fertility, perhaps even our intelligence, raising bioethical questions about the possibility of creating “designer” three-parent embryos (currently banned by the US FDA).