Gene Conversion During Primate Evolution

Abstract

Abstract Gene conversion is a nonreciprocal recombination process; the term originally referred to distorted segregation of alleles in gametocytes. In evolutionary studies, however, gene conversion often means ‘the transfer of deoxyribonucleic acid (DNA) sequence information from one locus to another’. In evolutionary processes, gene conversion is frequently observed between tandemly duplicated sequences or between homologous sequences on the same or on different chromosome(s). Gene conversion between functional loci has three significant roles: (1) Gene conversion generally works to maintain sequence and functional similarity in the ‘coevolution’ of interacting molecules. (2) Gene conversion often takes place between a functional gene and a pseudogene, and such events mainly cause diseases, especially in humans. Rarely, such conversions may confer a novel function to a converted gene. (3) Gene conversion erases advantageous sequence divergence between genes. In these cases, negative selection against for conversion maintains the advantageous divergence, and the converted genes are eliminated from a population. Key Concepts: Concerted evolution is one of evolutionary mechanisms acting on multigene families, and it maintains homogeneity among members of the family within a species. Coevolution at the molecular level means that two or more molecules that interact with each other evolve in a harmonious way. A nonprocessed pseudogene is a functionless gene caused by detrimental mutations such as nonsense mutations, frameshift mutations (causing a premature stop codon) or mutations in the regulatory region (silencing the expression). A processed pseudogene is a retrotransposed mRNA of a particular gene. They are randomly inserted into the genome and do not have regulatory elements; therefore, they usually are not expressed. Paralogues are homologous genes within a species that originate from gene duplication. Orthologues are homologous genes found in different species that are transmitted to daughter species during speciation. Gametologues are homologous genes on a pair of sex chromosomes, for example, the X and Y chromosomes in mammals or the Z and W chromosomes in birds.