Using Mitochondrial DNA to Measure Evolutionary Distance

Background: Mitochondrial DNA passes from mother to offspring with no hereditary input from the father. Only the female ovum contains mitochondria. The male sperm head contains no mitochondria. As a result, all individuals that can be traced back to a common female ancestor should have the same mitochondrial DNA (mtDNA). It has been demonstrated that mrDNA mutates at a rate about 10 times that of nuclear DNA. Such mutations result in differences between the mrDNA of individuals who share a common ancestral mother. By knowing the rate of mtDNA mutation and the actual number of differences between two related individuals, it is possible to calculate the approximate time since they shared a common female ancestor.