The world's first baby has been born using a new fertility technique that incorporates DNA from three people. The five-month-old boy has the usual DNA from his mother and father, plus a small amount of genetic code from a donor.
Doctors from the USA took the unprecedented step to ensure the baby boy would be free of a genetic condition that his Jordanian mother carries in her genes.
Experts say the move heralds a new era in medicine and could help other families with rare genetic conditions. It's not the first time scientists have created babies that have DNA from three people but it is a completely different technique.
But they warn that rigorous checks of this new and controversial technology, called mitochondrial donation, are needed. Mitochondria are tiny structures inside nearly every cell of the body that convert food into usable energy. Some women carry genetic defects in mitochondria and they can pass these on to their children.
In the case of the Jordanian family, it was a disorder called Leigh Syndrome that would have proved fatal to any baby conceived. The family had already experienced the heartache of four miscarriages as well as the death of two children, one at eight months and the other at six years of age.
The US team, who travelled to Mexico to carry out the procedure because there are no laws there that prohibit it, used a method that takes all the vital DNA from the mother's egg plus healthy mitochondria from a donor egg to create a healthy new egg that can be fertilised with the father's sperm.
The result is a baby with 0.1% of their DNA from the donor (mitochondrial DNA) and all the genetic code for things like hair and eye colour from the mother and father.
Dr John Zhang, medical director at the New Hope Fertility Centre in New York City, and his colleagues used the method to make five embryos but only one of them developed normally.
The UK has already passed laws to allow the creation of babies from three people. Professor Alison Murdoch, part of the team at Newcastle University that has been at the forefront of three person IVF work in the UK, said: "The translation of mitochondrial donation to a clinical procedure is not a race but a goal to be achieved with caution to ensure both safety and reproducibility."
Professor Darren Griffin, an expert in Genetics at the University of Kent, said: "This study heralds a new era in preimplantation genetics and represents a novel means for the treatment of families at risk of transmitting genetic disease.
"With radical new treatments like this there are always challenging ethical issues, however any concerns need to be balanced against the ramifications of not implementing such a technology when families are in need of it."
The procedure was revealed in an article in the New Scientist.