Mitotic recombination in the absence of synaptonemal complexes in Saccharomyces cerevisiae.

Mitotic cells of a diploid strain of Saccharomyces cerevisiae with appropriate markers for the detection of mitotic crossing-over and mitotic gene conversion were irradiated with X-rays. Induction of these recombinational events was strong. After irradiation, cells were incubated in a rich growth medium and samples were removed for studying the possible formation of synaptonemal complexes up to a time when most cells had completed the first post-irradiation cell division. No complexes were found during the entire period of sampling, during which mitotic recombination in G1 (mitotic gene conversion), DNA replication and G2 (mitotic crossing-over) had occurred. These results are interpreted to mean that synaptonemal complexes are not required for mitotic recombination.