Human Fertilisation and Embryology

As we have heard, mitochondrial DNA makes up a tiny proportion of our total DNA. Unlike nuclear DNA, it does not pass on any personal attributes; it is purely involved in the chemistry of energy production. That is why, when there is a defect in mitochondrial DNA, it tends to affect organs that require a high amount of energy, such as the heart, muscles, brain and liver. All of our mitochondria are inherited from the egg and, as we have heard, researchers have worked on techniques to replace faulty mitochondria using those from a healthy donor. To refer to that donor as a third parent, as some have, is something of a misnomer. There are 37 genes in mitochondrial DNA, which is less than 0.01% of our total DNA. Altering the mitochondria will not alter a child’s characteristics inherited from its biological parents, but it may provide a way to prevent a debilitating and sometimes fatal disease.