Abstract
In this article, we described the spontaneously occurring mutation specificities of defects that are involved in translesion polymerase, mutS mismatch correction and polA mismatch correction in Escherichia coli. We argue that 1) there is no contribution of translesion polymerase to E. coli chromosomal mutation, 2) mutS system recognizes and corrects transition and frameshift mismatches and 3) polA system recognizes and corrects deletion, frameshift and transition mismatches. We also characterized the genetic alterations that inactivate either the CAN1 gene of Saccharomyces cerevisiae haploid cells or heterozygously situated in diploid cells. The characteristics of mutation in haploid yeast are essentially consistent with those in E. coli, suggesting that similar mechanisms are operating to form spontaneous mutation. CAN1+/can1- (CanS) to can1-/can1- (CanR) mutations in diploid cells could occur through recombination, mainly allelic crossover and gene conversion.
