Definition: Mitochondrial inheritance is one of the ways in which diseases can be inherited from a parent. Most of our DNA is in the nucleus of our cells, but some is also included in the mitochondria. Mitochondrial DNA is inherited from our mothers only. If there is a mutation in a woman’s mitochondrial DNA, she will pass it on to each of her children. However, that condition will not necessarily have the same symptoms in each of her children because different amounts of normally working DNA and changed DNA may be inherited in each child, which affects the severity of the condition.