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J Hered. 2009 Sep-Oct; 100(5): 618–623.
Published online 2009 July 17. doi:  10.1093/jhered/esp056
PMCID: PMC2877545

Intron-Dominated Genomes of Early Ancestors of Eukaryotes


Evolutionary reconstructions using maximum likelihood methods point to unexpectedly high densities of introns in protein-coding genes of ancestral eukaryotic forms including the last common ancestor of all extant eukaryotes. Combined with the evidence of the origin of spliceosomal introns from invading Group II self-splicing introns, these results suggest that early ancestral eukaryotic genomes consisted of up to 80% sequences derived from Group II introns, a much greater contribution of introns than that seen in any extant genome. An organism with such an unusual genome architecture could survive only under conditions of a severe population bottleneck.

Keywords: effective population size, endosymbiosis, group II self-splicing introns, origin of eukaryotes, spliceosomal introns

Articles from Journal of Heredity are provided here courtesy of Oxford University Press