Mitochondrial DNA

Mitochondrial DNA (mtDNA, or less popularly, mDNA) is DNA which is not located in the nucleus of the cell but in the mitochondria. Mitochondria are parts of the cell that generate fuel in the form of adenosine triphosphate (ATP), which drives the varied machinery of the cell.

Mitochondrial inheritance

Mitochondria in mammalian sperm are usually destroyed by the egg cell after fertilization. In 1999 it was reported that paternal sperm mitochondria (containing mtDNA) 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. It has also been reported that mitochondria can occasionally be inherited from the father, e.g. in bananas (Schwartz and Vissing, 2002).

Related Topics:
1999 - Ubiquitin - Embryo - Banana

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The fact that mitochondrial DNA is maternally inherited enables researchers to trace uterine lineage far back in time. (Y chromosomal DNA, paternally inherited, is used in an analogous way to trace the agnate lineage.) This is accomplished in humans by sequencing one or more of the hypervariable control regions (HVR1 or HVR2) of the mitochondrial DNA. HVR1 consists of about 440 base pairs. These 440 base pairs are then compared to the control regions of other individuals (either specific people or subjects in a database) to determine maternal lineage. Most often, the comparison is made to the revised Cambridge Reference Sequence. Vilà et al have published studies tracing the matrilineal descent of domestic dogs to 4 individuals http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9180076. The concept of the Mitochondrial Eve is based on the same type of analysis, attempting to discover the origin of humanity by tracking the lineage back in time.

Related Topics:
Uterine - Y chromosomal DNA - Cambridge Reference Sequence - Mitochondrial Eve - Humanity

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See also: single origin theory.

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