Gene duplication: The formation of new genes… genes… genes

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Genes are the building blocks of all living organisms, but have you ever wondered: how are new genes made? Our Last Universal Common Ancestor (LUCA) had an estimated gene tally of 200-500. Yet, the human genome contains over 20,000 genes - how did they come from such a minimal source? Let’s uncover the key piece of this puzzle and scrutinise the secret ingredient of gene formation - gene duplication!
Gene duplication involves the copying of genetic information into two paralogs (gene duplicates). Mutations inevitably amass in either copy, due to genetic redundancy of duplicate loci. Between paralog copies, essential ancestral gene functions must be maintained, but new genes may also arise in either replica. If retaining both copies is advantageous to the organism, evolution will permanently fix duplicate loci. Who made this revolutionary proposition? Susumu Ohno, the ‘father’ of gene duplication! He outlined 3 mechanisms by which this phenomenon occurs, including neofunctionalisation.
At its time of publication, Ohno’s work was not widely accepted - alternative gene formation models were proposed. However, 1996 marked a momentous year in the genetic calendar. Sequencing the genome of Saccharomyces cerevisiae validated Ohno’s genius - genome duplication was found to be the source of its numerous paralogs. Decoding genomes revealed a factor Ohno could not yet accommodate - the complexity of eukaryotic regulatory regions. So, Allan Force and his genetic Jedi order proposed the Duplication Degeneration Complementation (DDC) model of gene preservation. DDC causes ‘partitioning’ of ancestral function, by degenerate mutations accumulating in protein-coding and regulatory regions. Since deleterious mutations are more probable than beneficial ones, DDC could help explain higher instances of paralog preservation in certain lineages. Ultimately, evidence exists for both DDC and Ohno’s model - the mechanism dependent upon gene complexity and population size. And maybe, just maybe, both mechanisms could occur simultaneously - subneofunctionalisation! Overall, the more genomes we sequence, the more we learn. For now, we know the recipe of gene formation is a multifaceted one.
Creator: Monica Harrison
References:
The last universal common ancestor between ancient Earth chemistry and the onset of genetics. Weiss MC, Preiner M, Xavier JC, Zimorski V, Martin WF. PLoS Genet. 2018 Aug; 14(8): e1007518. doi: 10.1371/journal.pgen.1007518
Evolution by gene duplication. Ohno S. Springer Berlin. 1970; 1. doi: 10.1007/978-3-642-86659-3.
The effects of unequal crossing over at the Bar locus in Drosophila Sturtevant AH. Genetics. 1925 Mar;10(2):117-47. doi: 10.1093/genetics/10.2.117.
The part played by recurrent mutation in evolution Haldane JBS. The American Naturalist. 1933; 67(708): 5-19. doi: 10.1086/280465.
Evolution and tinkering. Jacob F. Science. 1977 Jun 10;196(4295):1161-6. doi: 10.1126/science.860134.
Origin of genes. Gilbert W, de Souza SJ, Long M. Proc Natl Acad Sci U S A. 1997 Jul 22;94(15):7698-703. doi: 10.1073/pnas.94.15.7698.
Chromosome studies on normal and leukemic human leukocytes. Nowell PC, Hungerford DA. J Natl Cancer Inst. 1960 Jul;25:85-109.
Proof and evolutionary analysis of ancient genome duplication in the yeast Saccharomyces cerevisiae. Kellis M, Birren BW, Lander ES. Nature. 2004 Apr 8;428(6983):617-24. doi: 10.1038/nature02424.
Preservation of duplicate genes by complementary, degenerative mutations. Force A, Lynch M, Pickett FB, Amores A, Yan YL, Postlethwait J. Genetics. 1999 Apr;151(4):1531-45. doi: 10.1093/genetics/151.4.1531.
On the possibility of constructive neutral evolution. Stoltzfus A. J Mol Evol. 1999 Aug;49(2):169-81. doi: 10.1007/pl00006540.
Evolution of the differential regulation of duplicate genes after polyploidization. Ferris SD, Whitt GS. J Mol Evol. 1979 Apr 12;12(4):267-317. doi: 10.1007/BF01732026.
Role of positive selection in the retention of duplicate genes in mammalian genomes. Shiu SH, Byrnes JK, Pan R, Zhang P, Li WH. Proc Natl Acad Sci U S A. 2006 Feb 14;103(7):2232-6. doi: 10.1073/pnas.0510388103.
The origins of genome complexity. Lynch M, Conery JS. Science. 2003 Nov 21;302(5649):1401-4. doi: 10.1126/science.1089370.
Rapid subfunctionalization accompanied by prolonged and substantial neofunctionalization in duplicate gene evolution. He X. Zhang J. Genetics. 2005 Feb;169(2):1157-64. doi: 10.1534/genetics.104.037051. Epub 2005 Jan 16.
The altered evolutionary trajectories of gene duplicates. Lynch M, Katju V. Trends Genet. 2004 Nov;20(11):544-9. doi: 10.1016/j.tig.2004.09.001.