Age estimates of duplications: HSA 1/2/8/20 Paralogon

Identifying the timing of duplication events relative to radiation of taxa is critical to accurate and adequate cross-species comparisons. Major evolutionary scenarios that prompted novelties and explosion in gene number throughout animal genomes can be taken in view by relative dating of these events. For 11 multigene families with tripicated or quadruplicated representations on Hsa 1/2/8/20, the order of branching within the phylogenetic tree was used to estimate the time window of gene duplication events relative to the divergence of major taxa of organisms. This method of relative dating does not rely on the assumption of a constant rate of evolution. Therefore the process is sensitive to the varying rate of evolution in different branches of the tree (Hughes 1998). For 11 multigene families analyzed in this study, 6 duplication events were detected before the vertebrate–invertebrate split, 23 duplications were detected after vertebrate–invertebrate and before tetrapods–bony fish divergence whereas 10 duplication events were detected in teleosts (Abbasi and Hanif, 2012) (Figure 1).

 Figure 1: The relative timing of duplication events that expanded the multigene families residing on human 1/2/8/20 paralogon. 

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