week 14 Draft 4 "Yeast Genetics Lab"

Saccharomyces cerevisiae, a unicellular eukaryotic fungus also known as budding yeast, has two forms in which it can be in: haploid or diploid. Haploid form exists as one of the two mating types which is MATa or MAT and when together form diploid. In haploid form they can only survive in optimal nutrient-rich surroundings. When the diploid forms are in starvation, however, they can sporulate and become haploid once more with the production of ascus which protects the four haploid spores. When nutrients supply is restored then germination of the ascus and spores will occur. If not, then the ascus will remain intact until a favorable environmental condition is meet. Diploid and haploid yeast cells have the ability to undergo budding which is essentially cell division in yeast. (1) In Saccharomyces cerevisiae, the start of meiosis is controlled and regulated by mating type and nutritional conditions. This all occurs in MATa or MAT cells in nitrogen depletion media (Kassir et al. 2003). HB1, HA0, HA1, and HA2 were the haploid strains used with each containing its own characteristics. HB1 is mating type  with an ade mutation making it mutant deficit for adenine biosynthesis. HA0 is mating type a containing no mutations and has the ability to synthesize adenine.