Chemical genetics is the investigation of the function of proteins and signal transduction pathways in cells by the screening of chemical libraries of small molecules. Chemical genetics is analogous to classical genetic screen where random mutations are introduced in organisms, the phenotype of these mutants is observed, and finally the specific gene mutation (genotype) that produced that phenotype is identified. In chemical genetics, the phenotype is disturbed not by introduction of mutations, but by exposure to small molecule tool compounds. Phenotypic screening of chemical libraries is used to identify drug targets (forward genetics) or to validate those targets in experimental models of disease (reverse genetics). Recent applications of this topic have been implicated in signal transdu