of duplicate gene pairs of duplicate gene pairs what

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Unformatted text preview: no was correct!! there were 2 whole genome duplications, one on the way to bony fish and on the way to tetrapods. HOX genes were used to determine this. some large co- linear blocks of genes have 4x copy number in vertebrate lineages Phylogeny of Hox gene clusters in animals Unlikely that each gene duplicated independently, although pattern could arise by SD not WGD Dynamics of Gene Duplication If individual genes randomly duplicate and disappear over time, we expect there to be more young duplicates than old duplicates in a genome (old genes have more time to be lost and new duplicates present more substrates for duplications) This type of birth- death process, with constant rates of duplication and loss, would yield which one of these survivorship curves? older paralogs # of duplicate gene pairs younger paralogs % divergence ⇒ % divergence ⇒ % divergence ⇒ there will be less duplicants of new paralogs due to the birth death process. What about a WGD against a background of birth-death of individual duplciates? # of duplicate gene pairs # of duplicate gene pairs What does the distribution look like if there is a Whole Genome Duplication (WGD)? % divergence ⇒ % divergence ⇒ A Whole Genome Duplication will appear as a spike in the frequency distribution and also we might expect sets of duplicated genes to remain co-linear (syntenic) Fish should only have two copies of the genome if there have only been 2R rounds of genome duplication. However, we can see a recent duplication independent of the tetrapod replication that has occurred very recently. There was WGD in sh about 300 mya, after the lineage split from tetrapods If the 2R hypothesis of Ohno is correct, 1R 2R 1R 2R why do sh have 4 copies of the HOX gene cluster? 2R 1R The fate of duplicated genes 1. Nonfunctionalization: One copy becomes inactivated by mutation because there is no purifying selection to maintain it. 2. Neofunctional...
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