Forensics is another place where mtDNA comes in handy. At times, when the only evidence is tussue such as a strand of hair, solid bone or teeth, nuclear DNA cannot be tested because these tissues are low in usable nuclear DNA, but are abundant in mitochondrial DNA (Wallace, 26). However, when testing mitochondria DNA, if there is a match between two sources of mtDNA, one can conclude that it came from the same person. However, if the two sources do not match, it does not necessarily mean that the DNA came from two different people. Rather, it is inconclusive, because the sequence of mtDNA is not constant throughout a person's body, due to the higher mutation rate of mtDNA. In this case, it would seem that nuclear DNA is more reliable and more effective, because with nuclear DNA, it is possible to have a definite positive, or a definite negative. And in fact, nuclear DNA testing is preferable. However, when the only evidence available is low in nuclear DNA and high in mitochondrial DNA, then mtDNA testing must be used.
Understanding the mitochondria and its DNA is also important in understanding the evolution of the eukaryotic cell. In the late 1960's, when mtDNA was discovered, some researchers speculated that since mitochondria had their own DNA, they might be semi-independent organisms (Miller). This eventually gave rise to the Endosymbiont theory which hypothesizes that mitochondria and chloroplasts were once prokaryotic organisms which, over many years of evolution, developed a symbiotic relationship with eukaryotic cells (Melcher). Some properties of mitochondria and mtDNA are indeed very suggestive of this theory. First of all, mitochondria contain an outer membrane very similar to the plasma membrane (Gooch). Also, as discovered in the early 1960's mitochondria could not replicate"de novo" but rather they always came from the division of pre-existing mitochondria (Miller).