A PHYSICAL ASSAY FOR DETECTION OF EARLY MEIOTIC RECOMBINATION INTERMEDIATES IN SACCHAROMYCES-CEREVISIAE

In most eukaryotic organisms, recombination events leading to exchange s between homologous chromosomes link the homologs in a manner that al lows their proper attachment to the meiotic spindle. In the yeast Sacc haromyces cerevisiae these exchanges are initiated in early prophase a s double-strand breaks in the DNA. These breaks are processed through a series of intermediates to yield mature crossovers late in prophase. The following experiments were designed to monitor the appearance of the earliest recombinant DNA strands formed in this process. A polymer ase chain reaction assay was devised that allows the detection of reco mbinant strands at a known initiation site for meiotic recombination. The time and rate of appearance of recombinant strands was found to co incide with commitment to recombination, demonstrating that DNA strand s bearing sequences from both parental chromosomes are rapidly formed after the initiation of meiotic recombination.