title: The origin of subfunctions and modular gene regulation.
abstract: Evolutionary explanations for the origin of modularity in genetic and developmental pathways generally assume that modularity confers a selective advantage. However, our results suggest that even in the absence of any direct selective advantage, genotypic modularity may increase through the formation of new subfunctions under near-neutral processes. Two subfunctions may be formed from a single ancestral subfunction by the process of fission. Subfunction fission occurs when multiple functions under unified genetic control become subdivided into more restricted functions under independent genetic control. Provided that population size is sufficiently small, random genetic drift and mutation can conspire to produce changes in the number of subfunctions in the genome of a species without necessarily altering the phenotype. Extensive genotypic modularity may then accrue in a near-neutral fashion in permissive population-genetic environments, potentially opening novel pathways to morphological evolution. Many aspects of gene complexity in multicellular eukaryotes may have arisen passively as population size reductions accompanied increases in organism size, with the adaptive exploitation of such complexity occurring secondarily.
authors.affiliation: Benaroya Research Institute at Virginia Mason, Seattle, Washington 98101, USA. force@vmresearch.org
authors.forename: Allan
authors.initials: A
authors.lastname: Force
authors.forename: William A
authors.initials: WA
authors.lastname: Cresko
authors.forename: F Bryan
authors.initials: FB
authors.lastname: Pickett
authors.forename: Steven R
authors.initials: SR
authors.lastname: Proulx
authors.forename: Chris
authors.initials: C
authors.lastname: Amemiya
authors.forename: Michael
authors.initials: M
authors.lastname: Lynch
mesh_terms: D005075:Biological Evolution; D003627:Data Interpretation, Statistical; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation / Q000502:physiology*; D014644:Genetic Variation; D008957:Models, Genetic; D009154:Mutation; D011153:Population; D014157:Transcription Factors / Q000502:physiology*
chemical_list: D014157:Transcription Factors