Homoplasmy

Homoplasmy is a term used in genetics to describe a eukaryotic cell whose copies of mitochondrial DNA are all identical.[1] When in normal and healthy tissues, all cells are homoplasmic.[2] Homoplasmic mitochondrial DNA copies may be normal or mutated;[1] however, most mutations are heteroplasmic[3][2] (only occurring in some copies of mitochondrial DNA). It has been discovered, though, that homoplasmic mitochondrial DNA mutations may be found in human tumors.[4]

The term may also refer to uniformity of plant plastid DNA, whether occurring naturally or otherwise.

Inheritance

In almost every species, mitochondrial DNA is maternally inherited.[2] This means that all of the offspring of a female will have identical and homoplasmic mitochondrial DNA. It is very rare for females to pass on heteroplasmic or homoplasmic mutations because of the genetic bottleneck, where only a few out of many mitochondria actually are passed on to offspring.[2]

The mussel Mytilus edulis is an anomaly in terms of mitochondrial DNA inheritance. Unlike almost all animals, this species has biparental inheritance for mitochondrial DNA, meaning that both the male and the female contribute mitochondria to the offspring. This was discovered when researchers realized that most individuals of a Mytilus edulis population were heteroplasmic[5]

Mutations

Many diseases resulting from mutations in mitochondrial DNA are not inherited but developed as the untranslated region of mitochondrial DNA is thought to be particularly susceptible to mutation.[6]

Inherited Homoplasmic Diseases

Leber's Hereditary Optic Neuropathy[7]

See also

Notes and references

  1. 1 2 Heteroplasmy vs. Homoplasmy. University of Miami Faculty of Medicine. Accessed October 21, 2012.
  2. 1 2 3 4 Dimauro, Salvatore; Davidzon, Guido (2005). "Mitochondrial DNA and disease" (PDF). Annals of Medicine 37: 222–232. Retrieved February 7, 2016.
  3. ↑ Ballana, E., Govea, N., de Cid, R., Garcia, C., Arribas, C., Rosell, J. and Estivill, X. (2008), Detection of unrecognized low-level mtDNA heteroplasmy may explain the variable phenotypic expressivity of apparently homoplasmic mtDNA mutations. Hum. Mutat., 29: 248–257. doi: 10.1002/humu.20639. Accessed October 21, 2012.
  4. ↑ Coller HA, Khrapko K, Bodyak ND, Nekhaeva E, Herrero-Jimenez P, Thilly WG. "High frequency of homoplasmic mitochondrial DNA mutations in human tumors can be explained without selection." Nature Genetics 28, 2001 Jun; pp. 147-50. DOI 10.1038/88859. Accessed October 21, 2012.
  5. ↑ Hoeh, Walter R.; Blakley, Karen H.; Brown, Wesley M. (1991-01-01). "Heteroplasmy Suggests Limited Biparental Inheritance of Mytilus Mitochondrial DNA". Science 251 (5000): 1488–1490.
  6. ↑ "Mammalian mitochondrial genetics: heredity, heteroplasmy and disease" (PDF). ac.els-cdn.com. Retrieved 2016-02-08.
  7. ↑ "Mitochondrial DNA Mutation Associated with Leber's Hereditary Optic Neuropathy".
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