Yeasts are unicellular organisms from the kingdom Fungi. Saccharomyces cerevisiae is one species of yeast that can carry out either asexual reproduction by mitosis or sexual reproduction by meiosis. Budding in S. cerevisiae is a process where a small daughter cell forms as a bud on the parent cell. The bud contains a copy of the parent cell nucleus and it eventually separates from the parent cell to form a new cell. S. cerevisiae can exist in two forms: haploid cells or diploid cells. • Haploid cells can be one of two different mating types: a and α. • Haploid cells can only mate with other haploid cells of the opposite mating type. Fig. 2.1 shows the life cycle of S. cerevisiae with its asexual and sexual reproductive stages. Key: mating type a (a) mating type α [Figure 2.1]