Single-strand scissions of nuclear yeast DNA occur without meiotic recombination.

In meiotic cells of Saccharomyces cerevisiae, reduction in molecular weights of DNA in alkaline sucrose gradients is observed concomittantly with premeiotic DNA replication and with commitment to recombination. Following the completion of the latter processes, higher molecular weights are obtained. These single-stranded breaks are found in both old and newly synthesised strands. Similar scissions in DNA are also found in a temperature-sensitive mutant (cdc40/cdc40), which does not undergo commitment to recombination at the restrictive temperature, and in vegetative wild type cells that were previously exposed to sporulation medium. The suggestion that these scissions are the physical manifestation of commitment to recombination is therefore rejected.