Mitochondrial DNA

Mitochondrial DNA is the small circular chromosome found inside mitochondria. These organelles, found in most eukaryotic cells, are the powerhouse of the cell. The mitochondria, and thus mitochondrial DNA, are passed exclusively from mother to offspring through the egg cell.
Electron microscopy reveals mitochondrial DNA in discrete foci. Bars: 200 nm. (A) Cytoplasmic section after immunogold labelling with anti-DNA; gold particles marking mtDNA are found near the mitochondrial membrane (black dots in the upper right). (B) Whole mount view of cytoplasm after extraction with CSK buffer and immunogold labelling with anti-DNA; mtDNA (marked by gold particles) resists extraction. From Iborra et al., 2004.

Mitochondrial DNA (mDNA or mtDNA) is the DNA located in the mitochondria organelles in a eukaryotic cell that converts chemical energy from organic compounds into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the DNA contained in a eukaryotic cell; most of the DNA is in the cell nucleus, and, in plants and algae, the DNA also is found in plastids, such as chloroplasts. Mitochondrial DNA is responsible for coding of 13 essential subunits of the complex oxidative phosphorylation (OXPHOS) system which has a role in cellular energy conversion.

Human mitochondrial DNA was the first significant part of the human genome to be sequenced. This sequencing revealed that human mtDNA has 16,569 base pairs and encodes 13 proteins. As in other vertebrates, the human mitochondrial genetic code differs slightly from nuclear DNA.

Since animal mtDNA evolves faster than nuclear genetic markers, it represents a mainstay of phylogenetics and evolutionary biology. It also permits tracing the relationships of populations, and so has become important in anthropology and biogeography.

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