Infrequent Co-conversion of Markers Flanking a Meiotic Recombination Initiation Site in Saccharomyces cerevisiae

To study the mechanism of meiotic recombination in Saccharomyces cerevisiae, we examined recombination in an interval where the majority of events are initiated at a single hotspot for DNA double-strand breaks (DSBs), with little or no expected contribution by outside initiation events. This interval contained infrequently corrected palindromic markers 300 bp to the left and 600 bp to the right of the DSB hotspot. Conversion of single markers occurred frequently, while conversion of both markers occurred rarely, and many of the tetrads in which both markers converted were the products of multiple events. These data indicate that most meiotic recombination intermediates are asymmetrically positioned around the initiating DSB, with a short (