Duplication of Spindle Plaques and Integration of the Yeast Cell Cycle

Throughout he history of cell biology, the eukaryotic cell cycle has been subject o investiga-tion by a wide variety of techniques. Hartwell et al. (1970) have recently introduced the use of con-ditional mutants to the analysis of cell-cycle vents in the budding yeast Saccharomyces cerevisiae. This species is admirably suited not only to the genetic manipulation required for this approach but also to the application of molecular techniques to the characterization f its DNA (see Cryer et al., this volume; Petes et al., this volume). From the cytological view, however, the yeast cell cycle may seem superficially to lack homology with the cell cycle of higher eukaryotes. Asin the basidiomycetes and other ascomycetes, yeast lacks the highly