Three-parent babies could cure diseases
In this technique defective mitochondria in one egg cell is replaced with normal mitochondria from an egg cell from another woman. It's not quite exactly a genetic manipulation, but the substitute mitochondria is passed on from generation to generation. Some people worry about this paving the way for what is sometimes called designer babies where people manipulate the DNA in an embryo in order to produce desired traits in their offspring. As the guy in the video says, it's not fair to hold hostage those who will benefit from mitochondrial transfers to fears about a possible future where people routinely pick and choose the traits of their children. Quite frankly I'm not convinced that genetic manipulation is necessarily a bad thing.