Determination by Ammonium of the Manner of Yeast Nuclear Division

Abstract

ALTHOUGH it is questionable whether mitosis and meiosis in the classical sense occur in Saccharomyces cerevisiae¹, there is no doubt that the nuclear divisions observed are genetically equivalent to those of higher forms of life^2,3. In sporogenesis, spore walls enclose the haploid nuclei resulting from meiosis, and thus presence of spores in a cell demonstrates that meiosis has occurred. But absence of spores is inadequate evidence that meiosis has not occurred: following formation of the tetrad of haploid nuclei spore walls may conceivably fail to form. Thus although the proportion of sporulated cells in a population is easily determined without staining, a nuclear staining schedule must be utilized for reliable assessment of meiotic frequency. Environmental conditions favouring sporulation are known to differ in many respects from those that promote growth⁴. Comparison of the response of yeast sporulation and growth to nutritional and other factors may therefore help explain how the manner of division (mitosis or meiosis) is determined, provided that the treated cells are examined utilizing a nuclear staining technique.