Meiosis in Coprinus VII. The prekaryogamy S-phase and the postkaryogamy DNA replication in C. lagopus.

The kinetics of incorporation of 32P into DNA have unequivocally shown that the premeiotic S-phase in Coprinus lagopus occurs before the onset of karyogamy. It takes 8 h under the control conditions (25 degrees C with a 16 h light-8 h dark regime) but only 6 h under the arrest-release conditions. An important discovery in this study is that the initiation of premeiotic DNA replication is subject to an arrest by restrictive conditions (35 degrees C under a continuous light regime) whereas that of the mitotic replication is not. Once initiated, meiotic DNA replication can continue even under the restrictive conditions. Incorporation of 32P into DNA at pachytene is quite extensive. These replications are considered to be repair replications.