Introduction:

    Saccharomyces cerevisiae, also known as baker's yeast, is often used as a model system. This is because it is a single celled eukaryote that can exist in a haploid or diploid form. It is also used because it is a facultative anaerobe which means it can grown under aerobic and anaerobic conditions. The yeast genome is the first eukaryote to have its entire genome sequences and it also contains all the typical anti-oxidant genes found in all eukaryotes. 

    Oxidative stress occurs when an unstable molecule of oxygen oxidizes other molecules in the cell such as lipids, proteins, and DNA. Examples of these unstable reactive oxygen species are hydrogen peroxide, superoxide anion, and hydroxyl radical. These are formed by cell performing aerobic respiration. There are different factors in the cell that  combat the effects of the reactive oxygen species. The focus of this experiment was glucose 6-phosphate dehydrogenase (G6PD), which catalyzes the pentose phosphate pathway where ribose 5-phosphate and NADPH are formed. NADPH is a source of electrons used to reduce molecules that have been oxidized. The gene that encodes for G6PD is ZWF1 in Saccharomyces cerevisiae yeast.

    The purpose of this study was to investigate yeast genes functionally related to ZWF1 using microarray technology. Examples of genes functionally related to ZWF1 are pho85 which encodes for cyclin-dependent kinase, ZMS1 and ZMS2 which are plasmid genes that encode for potential zinc finger transcription factors. The hypothetical pathway for this experiment was: pho85 mutation --> increased activity of ZMS1 and ZMS2 --> increased activity of stress response genes --> suppression of ZWF1 mutant. 

     A DNA microarray is a tool that is used to analyze gene expression and consists of glass slide or small membrane which contains samples of many genes. A microarray works by utilizing the ability of a mRNA to hybridize to a DNA template. This allows scientists to determine expression levels of thousands of genes in a single experiment by measuring the amount of mRNA bound on each site of the array. In this experiment, 70mer oligos were used as the probes on the array. The cDNA is tagged with fluorescent dyes, most commonly used ones are Cy3 (green) and Cy5 (red) which are scanned with laser to show the levels of expression for a particular gene. In this study, a mutation of the ZMS1 gene was examined in comparison to a wild-type ZMS1 gene. The goal of the experiment  was to look at the differences in the expression profile between ΔZMS1, labeled with Cy3 dye (green), and wild-type ZMS1,labeled with Cy5 (red), using microarray analysis. It was hypothesized that the levels of gene expression for the ΔZMS1 mutant would be lower than in the wild-type.