An experimental system for the molecular analysis of the aging process : The budding yeast Saccharomyces cerevisiae

BAKERS ' yeast {Saccharomyces cerevisiae) is a microbial1 eukaryote that undergoes an asymmetric form of cell division called budding (Strathern et al., 1981, 1982). It exists exclusively in the unicellular state, but it can develop along one of three alternate pathways: mating (sexual conju-gation) in the case of haploid cells, the meiotic cell cycle (sporulation) in the case of diploids, and the mitotic cell cycle in both haploid and diploid cells. Because haploids and diploids can multiply vegetatively by mitotic cell division, both the haplophase and the diplophase can be stably main-tained. Yeast display limited nutritional requirements, and they can be cultured in synthetic medium containing only a carbon source, such as glucose, in addition to salts, trace elements, and vitamins. In a rich medium, the culture displays a generation time as short as 80 min, and larg