Newcastle University researchers have created human embryos containing DNA from two women and one man, a procedure that could potentially prevent conditions including epilepsy, diabetes and heart failure.

The preliminary research has raised concerns about the possibility of genetically modified babies, but the scientists say the embryos are still only primarily the product of one man and one woman. Neurogenetics professor Patrick Chinnery explained: “We are not trying to alter genes, we’re just trying to swap a small proportion of the bad ones for some good ones.”

The process aims to avoid passing onto children bad mitochondria genes, which are contained outside the nucleus in a normal female egg.