Mitochondrial DNA
Mitochondrial DNA was discovered in the 1960s by Margit M. K. Nass and Sylvan Nass by electron microscopy as DNase-sensitive threads inside mitochondria, and by Ellen Haslbrunner, Hans Tuppy and Gottfried Schatz by biochemical assays on highly purified mitochondrial fractions.
Human mitochondrial genetics
In humans, mitochondrial DNA (mtDNA) forms closed circular molecules that contain 16,569 DNA base pairs, with each such molecule normally containing a full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules, with the quantity ranging between 1 and 15. Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500.