The purpose of my research this summer has been to determine which genes in the yeast Saccharomyces cerevisiae are required to protect them from oxidative and methylation damage. The byproducts of cell metabolism of oxygen often cause damage to the cell's DNA in the form of mutations which can cause cancer. Similarly, methylation damage also causes mutations; it is studied as a carcinogen. In order to test the reactions of certain strains to oxidative and methylation damage, qualitative experiments involving gradient plates and quantitative experiments using dilution and plating techniques were utilized. Although the wild type (WT) yeast strain was sensitive to methyl methanesulfonate (MMS), the mag1 deletion strain, which is missing the gene that helps protect against methylation damage, was much more so. Also, both the WT and the mag1 yeast cells were not as sensitive to oxidative damage by the H2 O2, the rad9 and nat3 deletion strains were. Quantitative experiments with MMS performed on the WT and mag1 strains showed, once again, that the mag1 strain was much more sensitive to the MMS than the WT. These results suggest that the gene deleted in the mag1 strain of the yeast is important in protecting yeast cells from methylation damage. In the same manner, the gene deleted from the rad9 and nat3 strains protected the yeast cells from oxidative damage. These results suggest that within the wild type yeast cell, there may be systems responsible for protection against methylation and oxidative damage in the yeast cells. In the future, unknown deletion strains will be tested to obtain more knowledge about the genes within the yeast cell that protect it against methylation and oxidative damage. This investigation was supported by Research Grant CA-17395 from the National Insititutes of Health.