Poorly repaired mismatches in heteroduplex DNA are hyper-recombinagenic in Saccharomyces cerevisiae.
In yeast meiotic recombination, alleles used as genetic markers fall into two classes as regards their fate when incorporated into heteroduplex DNA. Normal alleles are those that form heteroduplexes that are nearly always recognized and corrected by the mismatch repair system operating in meiosis. High PMS (postmeiotic segregation) alleles form heteroduplexes that are inefficiently mismatch repaired. We report that placing any of several high PMS alleles very close to normal alleles causes hyperrecombination between these markers. We propose that this hyperrecombination is caused by the high PMS allele blocking a mismatch repair tract initiated from the normal allele, thus preventing corepair of the two alleles, which would prevent formation of recombinants. The results of three point crosses involving two PMS alleles and a normal allele suggest that high PMS alleles placed between two alleles that are normally corepaired block that corepair.
Manivasakam
P
P
Department of Genetics, University of Alberta, Edmonton, Canada. mani@mbcrr.harvard.edu
Rosenberg
S M
SM
Hastings
P J
PJ
D000483:Alleles; D001483:Base Sequence; D003434:Crossing Over, Genetic; D004260:DNA Repair; D004271:DNA, Fungal; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009692:Nucleic Acid Heteroduplexes; D009838:Oligodeoxyribonucleotides; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D004271:DNA, Fungal; D009692:Nucleic Acid Heteroduplexes; D009838:Oligodeoxyribonucleotides