Mitochondrial DNAMitochondrial DNA
which is located not in the nucleus
of the cell
but in the mitochondria
. It has been widely believed that mitochondrial DNA is always passed on to offspring solely by the mother, although it has been reported that it can also occasionally be inherited from the father (Schwartz and Vissing, 2002).
It appears that the mitochondria in mammalian sperm are usually destroyed by the egg cell after fertilization. In 1999 it was reported that paternal sperm mitochondria (containing mt DNA) are marked with ubiquitin to select them for later destruction inside the embryo (Sutovsky et. al. 1999). Occasionally this process goes wrong, for example in inter-species hybrids.
Mitochondrial DNA has been studied to trace lineage far back in time.
Svante Pääbo has published studies tracing the ancestry of domestic dogs to 4 individuals. The concept of the mitochondrial Eve is based on the same type of analysis.
See single origin theory.
- Marianne Schwartz and John Vissing, "Paternal Inheritance of Mitochondrial DNA", New England Journal of Medicine, Aug 22, 2002; 347:576-580. 
- "Mitochondria can be inherited from both parents", New Scientist article on Schwartz and Vissing's report; 
- Sutovsky, P., et. al. 1999. "Ubiquitin tag for sperm mitochondria." Nature 402(Nov. 25):371-372. Abstract available at  and discussed in .