The mitochondrial genome is the genetic material of the mitochondria. The mitochondria are organelles that reproduce themselves semi-autonomously within eukaryotic cells.
The genetic material forming the mitochondrial genome is similar in structure to that of the prokaryotic genetic material. The mitochondrial chromosome is a circular DNA molecule, but unlike prokaryotes it is much smaller and several copies are present. This similarity supports the hypothesis that mitochondria arose from intracellular bacterial symbiotes, i.e. the endosymbiotic theory.
Mitochondrial genetic diseases can affect both males and females, but in most sexually-reproducing species the mitochondria are inherited maternally. There are exceptions, including some gymnosperms which inherit mitochondria or chloroplasts paternally and some musselss that have paternal inheritance of mitochondria as high as 10%, but the rate of paternal inheritance in humans and mice is less than 10-4.[1] The human mitochondrial genome consists of 16,569 base pairs comprising only 37 genes. These encode 13 proteins, 22 tRNAs, and 2 rRNAs.[2]
Compared to the nuclear genome, the mitochondrial genome possesses some very interesting features:
- All the genes are carried on a single circular DNA molecule.
- The genetic material is not bounded by a nuclear envelope.
- The DNA is not packed into chromatin.
- The genome contains little non-coding DNA ("junk" DNA, or introns).
- Some codons do not follow the universal rules in translation. Instead they resemble those of purple non-sulfur bacteria.
- Some bases are considered part of two different genes: both as the last base of one gene and as the first base of the next gene.
See also
References
- ^ Zouros E, Freeman KR, Ball AO, Pogson GH. (1992). "Direct evidence for extensive paternal mitochondrial DNA inheritance in the marine mussel Mytilus". Nature 359 (6394): 412-4. doi:10.1038/359412a0. PMID 1357555.
- ^ Wallace DC. (1999). "Mitochondrial diseases in man and mouse". Science 283 (5407): 1482-8. doi:10.1126/science.283.5407.1482. PMID 10066162.
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