Kinetics of Mitosis in Yeasts

Abstract

WHILE differences of opinion still exist among yeast cytologists concerning the real significance of the vacuole and the chromosome number of different yeast species, it is clear from the work of De Lamater¹, Lietz², Winge and Roberts³, Lindegren et al. ⁴ and McClary et al. ⁵ that (a) during division the yeast nucleus resolves into chromosomes which can be identified by suitable techniques ; (b) the nuclear membrane persists throughout the division cycle, whereas in higher organisms the membrane disappears in the prophase and reforms in telophase; and (c) intra-nuclear mitosis is followed by a process of nuclear separation and movement into the daughter cell which simulates amitosis. Doubt whether nuclear division is amitotic^6,7 could thus arise when no distinction is made between the nuclear division proper and the transport of the daughter nucleus into the bud. We have studied the nuclear cytology of the vegetative diplophase of Saccharomyces cerevsae, Zygosaccharomyces priorianus and Schizosaccharomyces pombe, using a new technique⁸, and the course of mitosis and the mode of separation of daughter nuclei observed by us are described here.