Yeast Reproduction

Figure %: Life Cycle of Yeast

The different kinds of yeast most commonly reproduce by budding and fission, both forms of asexual reproduction. Budding occurs when a small portion of the cytoplasm of the parent cell becomes separated into small daughter cell. Fission involves an equal division of the cytoplasm into two daughter cells.

Yeast can also reproduce sexually, and usually do so under starvation conditions. Most yeast have two mating types. In the most commonly studied species, Saccharomyces cerevisiae, these are designated a and alpha. When yeast of opposite mating types meet, the cells fuse (plasmogamy), followed by the fusion of their nuclei (karyogamy). This diploid cell can produce more diploid cells by budding. Eventually, a diploid cell will become and ascus and enter meiosis. This produces four haploid nuclei that are then surrounded by thick protective coats and become spores. These spores are released and become new haploid cells.