2R hypothesis

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The 2R-hypothesis (from English 2 rounds hypothesis , 2-round hypothesis', also ohno hypothesis ) is a theory of the development of gene duplications in the genomes of vertebrates.

properties

Predicted pattern of position of paralogue genes in two genome duplications

The 2R hypothesis was put forward by Susumu Ohno in 1970 , but the name did not emerge until 1999. It says that in the course of evolution the genome of the early vertebrate precursors went through two rounds of genome duplication . Ohno based his hypothesis on the size of the genome and the number of isozymes , and later added the missing link in some paralog genes, which occurs when a gene is duplicated on the same DNA molecule, as a further argument . His observation was supported in 1993 by the characterization of paralogue genes in mice. The duplications probably took place after the vertebrates separated from the tunicates and Amphioxus , about 450 to 550 million years ago.

The opposite hypothesis, on the other hand, assumes a series of gene duplications with crossing-over .

Individual evidence

  1. ↑ a b Paramvir Dehal, Jeffrey L. Boore: Two rounds of whole genome duplication in the Ancestral Vertebrate. In: PLoS Biology. 3, 2005, p. E314, doi : 10.1371 / journal.pbio.0030314 .
  2. ↑ Ohno S (1970). Evolution by Gene Duplication. London: Allen and Unwin, ISBN 0-04-575015-7 .
  3. ↑ AL Hughes: Phylogenies of developmentally important proteins do not support the hypothesis of two rounds of genome duplication early in vertebrate history . In: Journal of molecular evolution . 48, No. 5, 1999, pp. 565-76. doi : 10.1007 / PL00006499 . PMID 10198122 .
  4. ↑ K Hokamp, ​​A McLysaght, KH Wolfe: The 2R hypothesis and the human genome sequence . In: Journal of structural and functional genomics . 3, No. 1-4, 2003, pp. 95-110. doi : 10.1023 / A: 1022661917301 . PMID 12836689 .
  5. ↑ W Makalowski: Are we polyploids? A brief history of one hypothesis . In: Genome Research . 11, No. 5, 2001, pp. 667-70. doi : 10.1101 / gr.188801 . PMID 11337465 .
  6. ^ LG Lundin: Evolution of the vertebrate genome as reflected in paralogous chromosomal regions in man and the house mouse . In: Genomics . 16, No. 1, April 1993, pp. 1-19. doi : 10.1006 / geno.1993.1133 . PMID 8486346 .
  7. ^ NH Putnam, T. Butts, et al .: The amphioxus genome and the evolution of the chordate karyotype. In: Nature. Volume 453, number 7198, June 2008, ISSN  1476-4687 , pp. 1064-1071, doi : 10.1038 / nature06967 . PMID 18563158 .
  8. ↑ AL Hughes: Phylogenies of developmentally important proteins do not support the hypothesis of two rounds of genome duplication early in vertebrate history . In: Journal of molecular evolution . 48, No. 5, May 1999, pp. 565-76. doi : 10.1007 / PL00006499 . PMID 10198122 .
  9. ↑ AL Hughes, R. Friedman: 2R or not 2R: testing hypotheses of genome duplication in early vertebrates. In: Journal of structural and functional genomics. Volume 3, Numbers 1-4, 2003, pp. 85-93, ISSN  1345-711X . PMID 12836688 .