Synthesis-dependent strand annealing in meiosis.
Recent studies led to the proposal that meiotic gene conversion can result after transient engagement of the donor chromatid and subsequent DNA synthesis-dependent strand annealing (SDSA). Double Holliday junction (dHJ) intermediates were previously proposed to form both reciprocal crossover recombinants (COs) and noncrossover recombinants (NCOs); however, dHJs are now thought to give rise mainly to COs, with SDSA forming most or all NCOs. To test this model in Saccharomyces cerevisiae, we constructed a random spore system in which it is possible to identify a subset of NCO recombinants that can readily be accounted for by SDSA, but not by dHJ-mediated recombination. The diagnostic class of recombinants is one in which two markers on opposite sides of a double-strand break site are converted, without conversion of an intervening heterologous insertion located on the donor chromatid. This diagnostic class represents 26% of selected NCO recombinants. Tetrad analysis using the same markers provided additional evidence that SDSA is a major pathway for NCO gene conversion in meiosis.
McMahill
Melissa S
MS
Committee on Genetics, University of Chicago, Chicago, Illinois, United States of America.
Sham
Caroline W
CW
Bishop
Douglas K
DK
D003434:Crossing Over, Genetic; D004261:DNA Replication; D045566:DNA, Cruciform / Q000378:metabolism; D008540:Meiosis; D008957:Models, Genetic; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics
D045566:DNA, Cruciform