Mitochondrial DNA is present in the mitochondria of every cell and even in those cells which do not have a nucleus. Mitochondrial DNA is inherited maternally but it is passed on to both daughters and sons. Therefore every child (male or female) of a particular woman has an exact copy of his or her mother’s mitochondrial DNA. The diagram below demonstrates the inheritance pattern of mitochondrial DNA. Those represented by a circle are female and those represented by a square are male. Those with the same color interior share the same mitochondrial DNA.

Since mitochondrial DNA mutations occur only once every 50 generations, a maternal line can be traced back many generations using mitochondrial DNA analysis. This technology can be very useful in immigration, genealogy cases or tribal enrollment cases when two or more individuals are trying to prove they are from the same maternal lineage.