16 High-Throughput Strain Construction and Systematic Synthetic Lethal Screening in

This chapter discusses an array-based synthetic lethal analysis approach, termed as “synthetic genetic array (SGA) analysis,” which is an automated method for constructing double mutants (or higher order allele combinations) and large-scale mapping of functional relationships between specific genes and pathways in yeast. In budding yeast, Saccharomyces cerevisiae, a complete set of gene deletion mutants has been constructed for each of the ˜6000 predicted genes in the genome, identifying ˜1000 essential genes and creating ˜5000 viable deletion mutants. The fact that over 80% of the predicted genes are not required for life reflects the robustness of biological circuits and may reflect cellular buffering against genetic variation. Hence, the collection of ˜5000 viable deletion mutants represents a valuable resource for systematic genetic analysis, providing the potential to examine 12.5 million different double-mutant combinations for a synthetic lethal or sick phenotype. When two genes show a synthetic lethal interaction, it often reflects that the gene products impinge on the same essential function, such that one pathway functionally compensates for, or buffers, the defects in the other. Thus, large-scale mapping of genetic interactions should provide a global view of functional relationships between genes and pathways.