DNA SYNTHESES IN COURSE OF MEIOTIC DEVELOPMENT IN NEUROSPORA-CRASSA

Nuclear DNA syntheses were measured microspectrophotometrically in course of meiotic nuclear development in N. crassa. The purpose of the study was to establish the timing of these DNA syntheses in relation to meiosis and in the formation of its final products in an ideal genetic material, where the products of the meiotic division are recovered and identified. Spectrophotometric analysis indicated that the last premeiotic DNA replication is completed before karyogamy; a postmeiotic DNA replication takes place at the tetrad of the nuclei level; and finally a 2nd postmeiotic DNA replication occurs in the ascospores resulting in 8 binucleated ascospores. The timing of postmeiotic replication is compatible with the models explaining gene conversion through the postulated mechanisms involving heteroduplex formation.