How a third parent’s DNA can prevent hereditary diseases like cancer in a baby

In the UK, eight children have thus far been born using the DNA of three people, a method known as mitochondria donation treatment (MDT). The families of the children, from under six months to over two years old, have had rare but fatal mitochondrial disorders for generations. The children are said to be happy and healthy. But what do we know about MDT? How can is stop genetic diseases from being passed down?

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