Chemistry or biology: which comes first after the genome is sequenced?

In drug discovery, chemical screening is performed after a proteinʹs function has been determined. By screening for ligands that alter the function of a cell or an organism, new proteins that participate in poorly understood biological processes can be identified. Genomic and expression-cloning technologies can rapidly identify the protein targets of these ligands, enhancing the power of chemical screening as a tool for the initial stages of biological discovery.