It sounds like some sort of dystopian dream, but if a team of scientists from the UK’s Human Fertilisation and Embryology Authority (HFEA) have their way—and it looks like they might—genetically modified “three-parent” embryos could be an available option in just a few years.
“Three-parent babies” isn’t a term the HFEA uses (it opts rather for “mitochondrial replacement”), and it’s not quite what it sounds; person number three doesn’t really get much of a look-in. They’d only contribute 0.1 percent of the kid’s DNA, and it wouldn’t be nuclear DNA—so it wouldn’t affect physical attributes like eye colour, or characteristics like intelligence, or whatever.
Mitochondrial replacement is essentially a proposed add-on to conventional in-vitro fertilisation (IVF). It’s targeted to women who are at risk of passing on mitochondrial disease to their kids if they have them naturally.
Mitochondria are present in a huge range of cells, and in simple terms they’re responsible for providing energy to the cell, converting energy from food into cell-powering ATP. But if there’s something wrong with a woman’s mitochondria, like faults in its DNA, that can cause genetic mitochondrial diseases that can be passed down to her children. The HFEA explains that one in 200 children are affected, and while some have no symptoms, others can suffer from a range of potentially severe conditions.
So the proposed solution: replace the woman’s defective mitochondria with someone else’s healthy mitochondria, i.e. a third person donor contributing to the baby mix alongside mum and dad. Sounds simple, right? And actually, the methods kind of are in theory. You take the nuclear DNA out of the woman’s egg and stick it in the cytoplasm of someone else’s egg that’s had its nuclear DNA removed but still contains the mitochondria. Then you add sperm and, voilà, it’s the birds and the bees as usual. Another option is similar, but swaps both parents' nuclear DNA into a new egg after its been fertilised.
For the rest of the story: http://motherboard.vice.com/read/the-uk-could-allow-three-parent-babies-in-two-years