Meiotic mismatch repair quantified on the basis of segregation patterns in Schizosaccharomyces pombe.
Hybrid DNA with mismatched base pairs is a central intermediate of meiotic recombination. Mismatch repair leads either to restoration or conversion, while failure of repair results in postmeiotic segregation (PMS). The behavior of three G to C transversions in one-factor crosses with the wild-type alleles is studied in Schizosaccharomyces pombe. They lead to C/C and G/G mismatches and are compared with closely linked mutations yielding other mismatches. A method is presented for the detection of PMS in random spores. The procedure yields accurate PMS frequencies as shown by comparison with tetrad data. A scheme is presented for the calculation of the frequency of hybrid DNA formation and the efficiency of mismatch repair. The efficiency of C/C repair in S. pombe is calculated to be about 70%. Other mismatches are repaired with close to 100% efficiency. These results are compared with data published on mutations in Saccharomyces cerevisiae and Ascobolus immersus. This study forms the basis for the detailed analysis of the marker effects caused by G to C transversions in two-factor crosses.
Schär
P
P
Institute of General Microbiology, University of Bern, Switzerland.
Munz
P
P
Kohli
J
J
D001203:Ascomycota / Q000235:genetics; D002842:Chromatids; D015825:Chromosomes, Fungal; D004260:DNA Repair / Q000235:genetics*; D004271:DNA, Fungal / Q000235:genetics; D008540:Meiosis / Q000235:genetics*; D009154:Mutation; D009692:Nucleic Acid Heteroduplexes; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics*; D013172:Spores, Fungal
D004271:DNA, Fungal; D009692:Nucleic Acid Heteroduplexes