In this text, leading researchers discuss the role that inducible proteins play in cellular metabolism and the approaches being used to delineate the underlying molecular events that lead to their synthesis. The use of both classical methods such as protein purification and characterization, as well as molecular methods such as the use of antisense DNA to down-regulate the synthesis of specific target enzymes, as approaches to investigate the role particular enzymes play in cellular metabolism are discussed. Other chapters discuss molecular approaches to the study of gene expression, the identification and characterization of trans-acting transcription factors and attempts to dissect other parts of the signal transduction pathway by the search for pathway mutants.