Three-person IVF: Defying disease or reckless research?

Sperm, egg...and egg? The UK is set to become the first country to allow "three-parent IVF", which entails using a tiny amount of donor cell material to facilitate pregnancy in women who carry genes for mitochondrial disease. Critics worry it hasn't been studied enough and paves the way for "designer babies." Proponents say it prevents families from passing on incurable diseases