Extranuclear inheritance

Extranuclear inheritance or cytoplasmic inheritance is the transmission of genes that occur outside the nucleus. It is found in most eukaryotes and is commonly known to occur in cytoplasmic organelles such as mitochondria and chloroplasts or from cellular parasites like viruses or bacteria.[1][2][3]

Organelles

Mitochondria are organelles which function to produce energy as a result of cellular respiration. Chloroplasts are organelles which function to produce sugars via photosynthesis in plants and algae. The genes located in mitochondria and chloroplasts are very important for proper cellular function, yet the genomes replicate independently of the DNA located in the nucleus, which is typically arranged in chromosomes that only replicate one time preceding cellular division. The extranuclear genomes of mitochondria and chloroplasts however replicate independently of cell division. They replicate in response to a cell's increasing energy needs which adjust during that cell's lifespan. Since they replicate independently, genomic recombination of these genomes is rarely found in offspring contrary to nuclear genomes, in which recombination is common. Mitochondrial disease are received from the mother, sperm does not contribute for it.

Parasites

Extranuclear transmission of viral genomes and symbiotic bacteria is also possible. An example of viral genome transmission is perinatal transmission. This occurs from mother to foetus during the perinatal period, which begins before birth and ends about 1 month after birth. During this time viral material may be passed from mother to child in the bloodstream or breastmilk. This is of particular concern with mothers carrying HIV or Hepatitis C viruses.[2][3] Examples of cytoplasmic [symbiotic] bacteria have also been found to be inherited in organisms such as insects and protists.[4]

Types

Three general types of extranuclear inheritance exist.

References

  1. 1.0 1.1 C. W. Birky, Jr. (1994). "Relaxed and stringent genomes: why cytoplasmic genes don't obey Mendel's laws". Journal of Heredity 85 (5): 355–366.
  2. 2.0 2.1 Sangeeta Jain, Nima Goharkhay, George Saade, Gary D. Hankins & Garland D. Anderson (2007). "Hepatitis C in pregnancy". American Journal of Perinatology 24 (4): 251–256. doi:10.1055/s-2007-970181.
  3. 3.0 3.1 Patrick Duff (1996). "HIV infection in women". Primary Care Update for OB/GYNS 3 (2): 45–49. doi:10.1016/S1068-607X(95)00062-N.
  4. Jan Sapp (2004). "The dynamics of symbiosis: an historical overview". Canadian Journal of Botany 82 (8): 1046–1056. doi:10.1139/b04-055.
  5. 5.0 5.1 C. William Birky, Jr., Robert L. Strausberg, Jean L. Forster & Philip S. Perlman (1978). "Vegetative segregation of mitochondria in yeast: estimating parameters using a random model". Molecular and General Genetics 158 (3): 251–261. doi:10.1007/BF00267196.
  6. Marianne Schwartz & John Vissing (2003). "New patterns of inheritance in mitochondrial disease". Biochemical and Biophysical Research Communications 310 (2): 247–251. doi:10.1016/j.bbrc.2003.09.037.
  7. C. W. Birky, Jr. (1995). "Uniparental inheritance of mitochondrial and chloroplast genes: mechanisms and evolution". Proceedings of the National Academy of Sciences USA 92 (25): 11331–11338. doi:10.1073/pnas.92.25.11331. PMC 40394. PMID 8524780.
  8. A. Katie Hanse, Linda K. Escobar, Lawrence E. Gilbert & Robert K. Jansen (2006). "Paternal, maternal, and biparental inheritance of the chloroplast genome in Passiflora (Passifloraceae): implications for phylogenic studies". Botany 94 (1): 42–46. doi:10.3732/ajb.94.1.42. PMID 21642206.

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