Pseudogene
File:Pseudogene illustration.pdf
Pseudogenes are genes that have lost their function. They have lost their gene expression in the cell or their ability to code protein.[1] The term was coined in 1977.[2]
Pseudogenes can result from mutations in a gene whose product is not needed for the survival of the organism. Although not protein-coding, the DNA of pseudogenes may be functional.[3] It may be similar to other kinds of non-coding DNA which have a regulatory role.
Most have some gene-like features. They lack protein-coding ability resulting from a variety of disabling mutations, or their inability to encode RNA (such as with rRNA pseudogenes).[4]
Pseudogenes are generally thought of as the last stop for genomic material that is to be removed from the genome,[5] so they are often labeled as junk DNA. Pseudogenes contain fascinating biological and evolutionary histories in their sequences. This is due to a pseudogene's shared ancestry with a functional gene. In the same way that Darwin thought of two species as having a shared common ancestry followed by millions of years of evolutionary divergence (see speciation), a pseudogene and its associated functional gene also share a common ancestor and have diverged as separate genetic entities over millions of years.
Pseudogene Media
These are examples of features that normal genes need. Pseudogenes superficially resemble normal genes but are nonfunctional because they have one or more of these defects.
Mechanism of classical and processed pseudogene formation
Processed pseudogene production
One way a pseudogene may arise
2 ways a pseudogene may be produced
BRAF pseudogene acts as a ceRNA
The proS loci in Mycobacterium leprae and M. tuberculosis, showing three pseudogenes (indicated by crosses) in M. leprae that still have functional homologs in M. tuberculosis. Homologous genes are indicated by identical colors and thin blue vertical bars. Modified after Cole et al. 2001.
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References
- ↑ Vanin EF. Processed pseudogenes: characteristics and evolution. Annu. Rev. Genet. 19 (1985). p. 253–72. doi:10.1146/annurev.ge.19.120185.001345.
- ↑ Jacq C; Miller J.R. Brownlee G.G.. A pseudogene structure in 5S DNA of Xenopus laevis. Cell 12 (1) (September 1977). p. 109–20. doi:10.1016/0092-8674(77)90189-1.
- ↑ Poliseno L. A coding-independent function of gene and pseudogene mRNAs regulates tumour biology. Nature 465 (7301) (2010). p. 1033–1038. doi:10.1038/nature09144.
- ↑ Herron, Jon C; Freeman, Scott. Evolutionary analysis (2007). Upper Saddle River, NJ: 4th ed, Pearson Prentice Hall. ISBN 978-0-13-227584-2. [1]
- ↑ Zheng D. et al 2007. Pseudogenes in the ENCODE regions: Consensus annotation, analysis of transcription, and evolution. Genome Res. 17 (6): 839–51. [2]