Cerevisiae Lab Report

Introduction
The purpose of this lab was to calculate and determine the optimal dosage of ultraviolet (UV) light to expose Saccharomyces cerevisiae (S. cerevisiae) to that would result in a survival rate of 20-40%. Saccharomyces cerevisiae commonly referred to as baker’s yeast is a single-celled eukaryote. Yeast is capable of growing as either a haploid or a diploid cell. The diploid cell can reproduce mitotically or sporulate, a process initiating meiosis and forming an ascus with four spores (Sacchromyces, 2014). Haploid cell reproduces through mitosis, but can also form a diploid cell by fusing with another haploid cell of the opposite mating type. S. Cerevisiae has two mating types 172 MATa ade2 his3 leu2 trp1 ura3 can1 and 196 MATɑ ade2
Each group had been assigned one of the two strains of the yeast for plating. Once the sample was obtained, the S. cerevisiae stock solution went through a set of serial dilutions. First, the stock solution was placed in a vortex machine to make sure the contents were thoroughly mixed. This process of vortexing occurred before every transfer of solution. Next, 100ul of the stock solution was added to a vial two that contained 9.9mL of diluted water (dH2O). 100ul of vial two was combined with 9.9mL of dH2O in vial three. Then, 100ul was taken from vial three and plated on yeast-extract-dextrose minus adenine agar plates (YED-). A hockey stick soaked in ethanol and heated with a Bunsen burner was used to spread the sample onto the plate. It is important to avoid long periods with the lids of the plates removed as this can cause contamination. The next step in the serial dilutions was to take 1mL of solution from vial three and mix it with 9 mL of dH2O in vial four before plating it. 1mL of vial four was then added to 9mL of dH2O and plated. All the plates were then stored upside down and incubated for 48 hours at 30°C. The resulting colony forming units (CFU) were then counted and averaged with the class data to calculate the stock solution