2R or not 2R: testing hypotheses of genome duplication in early vertebrates.

摘要: The widely popular hypothesis that there were two rounds of genome duplication by polyploidization early in vertebrate history (the 2R hypothesis) has been difficult to test until recently. Among the lines evidence adduced support this are relative size, gene number, and existence genomic regions putatively duplicated during polyploidization. availability sequence for a substantial portion human makes possible first rigorous tests hypothesis. Comparison family size invertebrate genomes shows no 4:1 ratio between vertebrates invertebrates. Furthermore, explicit phylogenetic topology expected from have revealed alternative topologies majority families. Likewise, analyses shown often include genes at different times over evolution life. thus can be decisively rejected. Rather, current favors model which tandem duplication, whether segments or individual genes, predominates.