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]Cite error: A <ref> tag is missing the closing </ref> (see the help page).
Types
Three general types of extranuclear inheritance exist.
- Vegetative segregation results from random replication and partitioning of cytoplasmic organelles. It occurs with chloroplasts and mitochondria during mitotic cell divisions and results in daughter cells that contain a random sample of the parent cell's organelles. An example of vegetative segregation is with mitochondria of asexually replicating yeast cells.[3]
- Uniparental inheritance occurs in extranuclear genes when only one parent contributes organellar DNA to the offspring. A classic example of uniparental gene transmission is the maternal inheritance of human mitochondria. The mother's mitochondria are transmitted to the offspring at fertilization via the egg. The father's mitochondrial genes are not transmitted to the offspring via the sperm. Very rare cases which require further investigation have been reported of paternal mitochondrial inheritance in humans, in which the father's mitochondrial genome is found in offspring.[4] Chloroplast genes can also inherit uniparentally during sexual reproduction. They are historically thought to inherit maternally, but paternal inheritance in many species is increasingly being identified. The mechanisms of uniparental inheritance from species to species differ greatly and are quite complicated. For instance, chloroplasts have been found to exhibit maternal, paternal and biparental modes even within the same species.[5][6]
- Biparental inheritance occurs in extranuclear genes when both parents contribute organellar DNA to the offspring. It may be less common than uniparental extranuclear inheritance, and usually occurs in a permissible species only a fraction of the time. An example of biparental mitochondrial inheritance is in the yeast Saccharomyces cerevisiae. When two haploid cells of opposite mating type fuse they can both contribute mitochondria to the resulting diploid offspring.[1][3]
References
- ^ a b 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.
- ^ 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.
- ^ a b 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.
- ^ 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.
- ^ 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.
- ^ A. Katie Hansen; Linda K. Escobar; Lawrence E. Gilbert; Robert K. Jansen (2007). "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.