A path for coevolution of recombinational DNA repair, transposition, and the common nucleotides

Abstract

Homologous genetic recombination is required for recombinational DNA repair, is involved in the successful segregation of chromosomes at cell division, and contributes to the generation of genetic diversity in all organisms. Whereas recombination is a key enabling mechanism in the continuing evolution of life on earth, it is widely believed to have originated in bacteria or their progenitors as a DNA repair Ž process Dougherty, 1955; Maynard Smith, 1978; Bernstein et al., 1985, 1988; Crow, 1988; Ghiselin, 1988; Maynard Smith, 1988; Potter and Dressler, 1988; Cox, 1991, 1993; Clark and Sandler, 1994; . Michod, 1995; Kuzminov, 1996 . A scenario is presented here for the stepwise development of very early recombinational DNA repair systems, the presumed antecedents of the homologous genetic recombination systems found today in all organisms. The scheme is built in part on functional constraints imposed on nucleic acid structure by a requirement for recombinational repair. These constraints may Ž . have helped to establish the GAT U C constellation of nucleotides as the standard components of nucleic