title: Evolution of repeated DNA sequences by unequal crossover.
abstract: It is often supposed that highly repetitious DNA's arise only as a result of unusual mechanisms or in response to selective pressure. My arguments and simulations suggest, by contrast, that a pattern of tandem repeats is the natural state of DNA whose sequence is not maintained by selection. The simulations show that periodicities can develop readily from nonreptitious DNA as a result of the random accumulation of random mutations and random homology-dependent unequal crossovers. The lengths of these periodicities, and the patterns of subrepeats within them, would fluctuate in evolution, with the probability of a given pattern being dependent on the unknown exact nature of the crossover mechanism. Qualitatively, then, unequal crossover provides a reasonable and uncontrived explanation for the prevalence of highly repeated sequences in DNA and for the patterns of periodicity they evince.
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002842:Chromatids; D003201:Computers; D003434:Crossing Over, Genetic; D004247:DNA; D004276:DNA, Satellite; D005796:Genes; D008954:Models, Biological; D009154:Mutation; D012335:RNA, Ribosomal
chemical_list: D004276:DNA, Satellite; D012335:RNA, Ribosomal; D004247:DNA