Abstract
BackgroundThe hypothesis that vertebrates have experienced two ancient, whole genome duplications (WGDs) is of central interest to evolutionary biology and has been implicated in evolution of developmental complexity. Three-way and Four-way paralogy regions in human and other vertebrate genomes are considered as vital evidence to support this hypothesis. Alternatively, it has been proposed that such paralogy regions are created by small-scale duplications that occurred at different intervals over the evolution of life.ResultsTo address this debate, the present study investigates the evolutionary history of multigene families with at least three-fold representation on human chromosomes 1, 2, 8 and 20. Phylogenetic analysis and the tree topology comparisons classified the members of 36 multigene families into four distinct co-duplicated groups. Gene families falling within the same co-duplicated group might have duplicated together, whereas genes belong to different co-duplicated groups might have distinct evolutionary origins.ConclusionTaken together with previous investigations, the current study yielded no proof in favor of WGDs hypothesis. Rather, it appears that the vertebrate genome evolved as a result of small-scale duplication events, that cover the entire span of the animals’ history.
Highlights
The hypothesis that vertebrates have experienced two ancient, whole genome duplications (WGDs) is of central interest to evolutionary biology and has been implicated in evolution of developmental complexity
For investigating the validity of whole genome duplications (WGDs) hypothesis, which strongly supports that fourfold paralogons in the human genome had been formed by polyploidization events, we undertook phylogenetic analyses for 25 gene families
Each of these chosen subset of multigene families have at least threefold portrayal on one of the paralogy regions in human genome that comprises of segments from human chromosomes 1, 2, 8 and 20 (Fig. 1; Table 1)
Summary
The hypothesis that vertebrates have experienced two ancient, whole genome duplications (WGDs) is of central interest to evolutionary biology and has been implicated in evolution of developmental complexity. To elucidate the genetic underpinnings of major changes in organismal make up and the origination of ample new traits during the evolutionary history of vertebrates, Susumu Ohno in the year 1970 put forward the hypothesis that two rounds of whole genome duplications (WGDs) occurred early in vertebrate evolution. This hypothesis is popularly termed as “2R hypothesis” (two rounds of WGDs) and is believed to be the most rational. Phylogenetic data clarifies that the tetra-paralogy blocks on the human genome have resulted from independent duplications, segmental duplications and genomic restructuring events that had occurred at broadly different time points during the course of animal evolution
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