Cytology of the Yeast Life Cycle

INTRODUCTION The preceding papers in this volume clarify the major reasons that Saccharomyces cerevisiae is exceptionally well-suited to the analysis of cellular functions. The facility and rigor of its genetic analysis enable the researcher to apply the power of molecular genetics to the analysis of a wide variety of biochemical and cytological processes. One hopes, of course, that many of the processes revealed in yeast will provide clues to mechanisms operating in a broader range of eukaryotic organisms. Any similarities between processes occurring in yeasts and those in plant or animal cells may indicate useful experimental approaches for the latter organisms, which are less amenable to genetic analysis. In contrast, any differences should aid in defining those mechanisms that are fundamental to the eukaryotic mode of cellular function. Accordingly, this paper describes certain aspects of yeast cytology in comparison with our current understanding of other eukaryotic cells. In keeping with the central importance of genetics to our study of yeast, I have chosen to stress cytological aspects that are most pertinent to the transmission of the genetic material: mitosis, conjugation, and meiosis. This approach will necessitate omission of a wealth of other cytological information. Many topics, including important early observations from freeze-fracture preparation for electron microscopy, are described in the seminal review by Matile et al. (1969). In more recent reviews, Hartwell (1974) and Pringle and Hartwell (this volume) discuss observations on cytological changes in the cell-division cycle, and Cabib (1975) and Ballou (1982) describe the structure and formation of...