Revealing Retention Mechanisms of Duplicated Genes and Surveying Triple Mutant Genetic Interaction Space in Yeast

Recent genome sequencing efforts have revealed astounding genetic diversity between individuals in the human population. The current challenge is to assign functions to the thousands of genes in our genomes and to understand how individual differences in genes contribute to disease. Much progress has been made in identifying causal loci of single gene disorders for both common and rare genetic diseases. However, many phenotypes are influenced by more complex genetic interactions involving larger sets of genes and genetic variants. Thus, deciphering the genotype-phenotype relationship requires that we expand our focus beyond pair- wise genetic interactions to include complex, higher-order genetic interactions involving more than two genes. In this thesis I used the simple model organism, the budding yeast, and a method for automated yeast genetics called Synthetic Genetic Array (SGA) analysis, to construct double and triple mutants, and to measure the resulting genetic interactions by using colony size as a proxy for cell fitness. I first applied this methodology to dissect and characterize the mechanisms of functional divergence of duplicated genes. I also applied it more generally to estimate the prevalence of complex genetic interactions in a eukaryotic cell. My results suggest that triple mutant genetic interactions occur frequently in the yeast genome and are therefore expected to have a major impact on our understanding of the relationship between genotype and phenotype. This map of complex genetic interactions provides a unique dataset for studying how the content of our genomes is shaped and how this relates to complex disease.Ph.D.2017-07-08 00:00:0