British scientists say they have created human embryos containing DNA from two women and a man in a procedure that researchers hope might be used one day to produce embryos free of inherited diseases.
Though the preliminary research has raised concerns about the possibility of genetically modified babies, the scientists say that the embryos are still only primarily the product of one man and one woman.
"We are not trying to alter genes, we're just trying to swap a small proportion of the bad ones for some good ones," said Patrick Chinnery, a professor of neurogenetics at Newcastle University who was involved in the research.
The research was presented at a scientific conference recently but has not been published in a scientific journal.
The process aims to create healthy embryos for couples to avoid passing on genes carrying diseases.
The genes being replaced are the mitochondria—a cell's energy source—which are contained outside the nucleus in a normal female egg. Mistakes in the mitochondria's genetic code can result in serious diseases like muscular dystrophy, epilepsy, strokes, and mental retardation.
In their research, Chinnery and colleagues used normal embryos created from one man and one woman that had defective mitochondria in the woman's egg. They then transplanted that embryo into an emptied egg donated from a second woman who had healthy mitochondria.
The research is being funded by the Muscular Dystrophy Campaign, a British charity.
Not "Three Parents"
Only trace amounts of a person's genes come from the mitochondria, and experts said it would be incorrect to say that the embryos have three parents.
"Most of the genes that make you who you are are inside the nucleus," Chinnery said. "We're not going anywhere near that."