# Functional divergence

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**Functional divergence** is the process by which genes, after [gene duplication](/source/Gene_duplication), shift in function from an ancestral function. Functional divergence can result in either [subfunctionalization](/source/Subfunctionalization), where a paralog specializes one of several ancestral functions, or [neofunctionalization](/source/Neofunctionalization), where a totally new functional capability evolves. It is thought that this process of gene duplication and functional divergence is a major originator of molecular novelty and has produced the many large [protein families](/source/Protein_families) that exist today.[1][2]

Functional divergence is just one possible outcome of [gene duplication](/source/Gene_duplication) events. Other fates include [nonfunctionalization](/source/Nonfunctionalization) where one of the [paralogs](/source/Paralogs) acquires [deleterious](/source/Deleterious) [mutations](/source/Mutations) and becomes a [pseudogene](/source/Pseudogene) and [superfunctionalization](/source/Superfunctionalization) (reinforcement),[3] where both paralogs maintain original function. While gene, chromosome, or whole genome duplication events are considered the canonical sources of functional divergence of [paralogs](/source/Paralogs), [orthologs](/source/Orthologs) (genes descended from speciation events) can also undergo functional divergence [4][5][6][7] and [horizontal gene transfer](/source/Horizontal_gene_transfer) can also result in multiple copies of a gene in a genome, providing the opportunity for functional divergence.

Many well known protein families are the result of this process, such as the ancient gene duplication event that led to the divergence of [hemoglobin](/source/Hemoglobin) and [myoglobin](/source/Myoglobin), the more recent duplication events that led to the various subunit expansions (alpha and beta) of vertebrate [hemoglobins](/source/Hemoglobin),[8] or the expansion of G-protein alpha subunits [9]

## See also

- [Heterotachy](/source/Heterotachy)
- [Subfunctionalization](/source/Subfunctionalization)
- [Neofunctionalization](/source/Neofunctionalization)

## References

1. Gu, X (Jul 2003). "Functional divergence in protein (Family) sequence evolution". *Origin and Evolution of New Gene Functions*. *Genetica*. **118** (2–3): 133–41. Contemporary Issues in Genetics and Evolution. [doi:10.1007/978-94-010-0229-5_4](https://doi.org/10.1007/978-94-010-0229-5_4). ISBN 978-94-010-3982-6. [PMID 12868604](https://pubmed.ncbi.nlm.nih.gov/12868604)

1. Fay, JC & Wu, CI (2003). "Sequence divergence, functional constraint, and selection in protein evolution". *Annu Rev Genom Hum Genet*. **4**: 213–35. [doi:10.1146/annurev.genom.4.020303.162528](https://doi.org/10.1146/annurev.genom.4.020303.162528). [PMID 14527302](https://pubmed.ncbi.nlm.nih.gov/14527302)

1. Dvornyk, V; Vinogradova, ON; Nevo, E (2002). "Long-term microclimatic stress causes rapid adaptive radiation of kaiABC clock gene family in a cyanobacterium, Nostoc linckia, from "Evolution Canyons" I and II, Israel". *Proc Natl Acad Sci USA*. **99** (4): 2082–2087. [Bibcode:2002PNAS...99.2082D](https://ui.adsabs.harvard.edu/abs/2002PNAS...99.2082D). [doi:10.1073/pnas.261699498](https://doi.org/10.1073/pnas.261699498). [PMC 123721](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC123721). [PMID 11842226](https://pubmed.ncbi.nlm.nih.gov/11842226)

1. Studer, RA & Robinson-Rechavi, M (2009). ["How confident can we be that orthologs are similar, but paralogs differ?"](https://serval.unil.ch/notice/serval:BIB_39F8106EE698). *Trends in Genetics*. **25** (5): 210–6. [doi:10.1016/j.tig.2009.03.004](https://doi.org/10.1016/j.tig.2009.03.004). [PMID 19368988](https://pubmed.ncbi.nlm.nih.gov/19368988)

1. Studer & Robinson-Rechavi, M (2010). "Large-scale analysis of orthologs and paralogs under covarion-like and constant-but-different models of amino acid evolution". *Molecular Biology and Evolution*. **27** (11): 2618–2627. [doi:10.1093/molbev/msq149](https://doi.org/10.1093/molbev/msq149). [PMC 2955734](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2955734). [PMID 20551039](https://pubmed.ncbi.nlm.nih.gov/20551039)

1. Gharib, WH & Robinson-Rechavi, M (2011). "When orthologs diverge between human and mouse". *Briefings in Bioinformatics*. **12** (5): 436–441. [doi:10.1093/bib/bbr031](https://doi.org/10.1093/bib/bbr031). [PMC 3178054](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3178054). [PMID 21677033](https://pubmed.ncbi.nlm.nih.gov/21677033)

1. Nehrt, NL; Clark, WT; Radivojac, P; Hahn, MW (2011). "Testing the ortholog conjecture with comparative functional genomic data from mammals". *PLOS Computational Biology*. **7** (6). [Bibcode:2011PLSCB...7E2073N](https://ui.adsabs.harvard.edu/abs/2011PLSCB...7E2073N). [doi:10.1371/journal.pcbi.1002073](https://doi.org/10.1371/journal.pcbi.1002073). [PMC 3111532](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3111532). [PMID 21695233](https://pubmed.ncbi.nlm.nih.gov/21695233)

1. Storz, Jay F.; Hoffmann, Federico G.; Opazo, Juan C.; Moriyama, Hideaki (March 2008). "Adaptive Functional Divergence Among Triplicated α-Globin Genes in Rodents". *Genetics*. **178** (3): 1623–1638. [doi:10.1534/genetics.107.080903](https://doi.org/10.1534/genetics.107.080903). [PMC 2278084](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2278084). [PMID 18245844](https://pubmed.ncbi.nlm.nih.gov/18245844)

1. Zheng, Y; Xu, D; Gu, X (2007). ["Functional divergence after gene duplication and sequence-structure relationship: a case study of G-protein alpha subunits"](https://lib.dr.iastate.edu/rtd/15063). *Journal of Experimental Zoology Part B: Molecular and Developmental Evolution*. **308** (1): 85–96. [doi:10.1002/jez.b.21140](https://doi.org/10.1002/jez.b.21140). [PMID 17094082](https://pubmed.ncbi.nlm.nih.gov/17094082)

- Gu, X (Oct 2006). "A simple statistical method for estimating type-II (cluster-specific) functional divergence of protein sequences". *Mol Biol Evol*. **23** (10): 1937–45. [doi:10.1093/molbev/msl056](https://doi.org/10.1093/molbev/msl056). [PMID 16864604](https://pubmed.ncbi.nlm.nih.gov/16864604)

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