Difference between revisions of "Pseudogene"
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| − | '''Pseudogenes''' are genes present in an organism's [[genome]] that have lost the ability to code for proteins due to mutation. <ref name=petrov>Petrov, D.A, Hartl, D.L. (2000). Pseudogene evolution and natural selection for a compact genome. The American Genetic Association 91:221-227. [http://www.stanford.edu/group/petrov/research/16.pdf]</ref> They were first identified and dubbed in the late 1970s when researchers began finding non-coding regions in some organisms that were similar to actual coding genes in other organisms. <ref name=sciam>Gerstein, M, Zheng, D. (2006). The real life of pseudogenes. Scientific American 95:48-55. [http://papers.gersteinlab.org/e-print/sciam2/preprint.pdf]</ref> So far an estimated 19,000 pseudogenes have been identified in the human genome, this is almost equal to the total number of coding genes (21,000). <ref name=sciam /> Pseudogenes have been identified in a wide range of organisms from bacteria to mice to humans, the total number of pseudogenes in a given genome is not predictable but specific pseudogenes are often compared across species to elucidate complex evolutionary relationships <ref name=sciam /> Humans have many pseudogenes including [[L-gulonolactone oxidase]] which is used to synthesize vitamin c | + | '''Pseudogenes''' are genes present in an organism's [[genome]] that have lost the ability to code for proteins due to mutation. <ref name=petrov>Petrov, D.A, Hartl, D.L. (2000). Pseudogene evolution and natural selection for a compact genome. The American Genetic Association 91:221-227. [http://www.stanford.edu/group/petrov/research/16.pdf]</ref> They were first identified and dubbed in the late 1970s when researchers began finding non-coding regions in some organisms that were similar to actual coding genes in other organisms. <ref name=sciam>Gerstein, M, Zheng, D. (2006). The real life of pseudogenes. Scientific American 95:48-55. [http://papers.gersteinlab.org/e-print/sciam2/preprint.pdf]</ref> So far an estimated 19,000 pseudogenes have been identified in the human genome, this is almost equal to the total number of coding genes (21,000). <ref name=sciam /> Pseudogenes have been identified in a wide range of organisms from bacteria to mice to humans, the total number of pseudogenes in a given genome is not predictable but specific pseudogenes are often compared across species to elucidate complex evolutionary relationships <ref name=sciam /> Humans have many pseudogenes including [[L-gulonolactone oxidase]] which is used to synthesize vitamin c. |
==Finding pseudogenes== | ==Finding pseudogenes== | ||
Revision as of 02:59, April 5, 2007
Pseudogenes are genes present in an organism's genome that have lost the ability to code for proteins due to mutation. [1] They were first identified and dubbed in the late 1970s when researchers began finding non-coding regions in some organisms that were similar to actual coding genes in other organisms. [2] So far an estimated 19,000 pseudogenes have been identified in the human genome, this is almost equal to the total number of coding genes (21,000). [2] Pseudogenes have been identified in a wide range of organisms from bacteria to mice to humans, the total number of pseudogenes in a given genome is not predictable but specific pseudogenes are often compared across species to elucidate complex evolutionary relationships [2] Humans have many pseudogenes including L-gulonolactone oxidase which is used to synthesize vitamin c.
Finding pseudogenes
Pseudogenes are often difficult to parse from the large amount of non-coding base pairs in the genome. Convention requires two elements to be present to label a sequence a pseudogene. The first is homology which is the requirement that a sequence be demonstrated to descend from a functional copy of the gene and the second is non-functionality which is the requirement that the gene not code for a protein in the organism in question. [2]
Since all pseudogenes are descended from a functioning gene the first step is to find the parent gene that it descended from. This is done by using computer programs to compare sequences of DNA across species. [2] This is a large computational problem but by keeping in mind the phylogenetic relationships between species the search time can be decreased by looking at species that share a more recent common ancestor.[3] Once a functioning copy of a gene is detected its sequence is compared to the pseudogene. A high correlation in base pairs is used to assign homology. Non-functionality can be demonstrated by attempting to transcribe the sequence in-vitro. [2]
Pseudogenes and neutral selection theory
Because pseudogenes do not code for a function many scientist have hypothesized that the accumulation of mutations would not be constrained by selection pressures.[1] This is known as neutral selection, and pseudogenes have been studied extensively to test various theories of neutral selection. [4] It has been determined that mutations fixate in pseudogene regions at about 30 percent higher than in coding regions of DNA. [4] Some theorist have argued that there maybe some selection pressure on pseudogenes (such as on genome size in general) so conclusions should be tempered.[1] Others have determined that base pair mutations are not completely random, favoring accumulation of guanin and cytosine. [4] Despite these findings research on pseudogenes still continues to be a productive avenue for exploring mutation and selection.
See also
References
- ↑ 1.0 1.1 1.2 Petrov, D.A, Hartl, D.L. (2000). Pseudogene evolution and natural selection for a compact genome. The American Genetic Association 91:221-227. [1]
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Gerstein, M, Zheng, D. (2006). The real life of pseudogenes. Scientific American 95:48-55. [2]
- ↑ Bensasson, D., Zhang, D., Hartl, D., Hewitt, G. (2001). Mitochondrial pseudogense: evolution's misplaced witness. Trends in Ecology and Evolution 16: 314-321. [3]
- ↑ 4.0 4.1 4.2 Bustamante, C, Neilsen R, Hartl, D. (2002). A maximum likelihood method for analyzing pseudogene evolution: implications for silent site evolution in humans and rodents. 19:110-117. [4]