title: Intron-dominated genomes of early ancestors of eukaryotes.
abstract: 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.
authors.affiliation: National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA. koonin@ncbi.nlm.nih.gov
authors.forename: Eugene V
authors.initials: EV
authors.lastname: Koonin
mesh_terms: D005057:Eukaryotic Cells / Q000502:physiology*; D019143:Evolution, Molecular; D016678:Genome; D007438:Introns / Q000235:genetics*; D012326:RNA Splicing; D017381:Spliceosomes / Q000235:genetics; D013559:Symbiosis / Q000235:genetics