Meiosis in Schizophyllum commune: The effect of hydroxyurea on the frequency of recombination and mutations.

The effect of exposure of nuclei at different stages of meiosis to hydroxyurea (HU) was tested by examination of its effect on the frequency of auxotrophic mutations and on intergenic recombination. The results indicate that recombination is increased most significantly if the nuclei are exposed to the drug during the premeiotic-S phase and to a lesser extent if exposed during prophase. Similarly, nuclei exposed to HU during premeiotic-S phase and prophase mutate at a frequency 10 to 50 times higher than untreated meiotic nuclei. The degree of response of the mutagenic events and recombination events is not similar and it is suggested that the mutagenic events occur at stages prior to recombination. The temporal relations of the two events in response to HU suggest that the mutagenic events precede recombination and the results obtained with HU only amplify the mutagenic events that normally occur in meiotic nuclei and are related to the meiotic effect.