title: Numerous groups of chromosomal regional paralogies strongly indicate two genome doublings at the root of the vertebrates.
abstract: The appearance of the vertebrates demarcates some of the most far-reaching changes of structure and function seen during the evolution of the metazoans. These drastic changes of body plan and expansion of the central nervous system among other organs coincide with increased gene numbers. The presence of several groups of paralogous chromosomal regions in the human genome is a reflection of this increase. The simplest explanation for the existence of these paralogies would be two genome doublings with subsequent silencing of many genes. It is argued that gene localization data and the delineation of paralogous chromosomal regions give more reliable information about these types of events than dendrograms of gene families as gene relationships are often obscured by uneven replacement rates as well as other factors. Furthermore, the topographical relations of some paralogy groups are discussed.
authors.affiliation: Department of Neuroscience, BMC, Uppsala University, S-751 24 Uppsala, Sweden. lglundin@neuro.uu.se
authors.forename: Lars-Gustav
authors.initials: LG
authors.lastname: Lundin
authors.forename: Dan
authors.initials: D
authors.lastname: Larhammar
authors.forename: Finn
authors.initials: F
authors.lastname: Hallböök
mesh_terms: D000818:Animals; D005075:Biological Evolution; D007446:Chromosome Inversion; D002874:Chromosome Mapping; D020440:Gene Duplication; D020868:Gene Silencing; D016678:Genome; D010802:Phylogeny; D026801:Synteny; D014178:Translocation, Genetic; D014714:Vertebrates / Q000235:genetics*