Enzyme induction occurs when a molecule like a drug binds to and increases the metabolic activity of an enzyme, causing it to be expressed at higher levels. This allows enzymes to kick into production when needed. Enzyme repression is when an effector binds to the operator of a gene and prevents the binding of RNA polymerase, reducing expression of the enzyme. Understanding enzyme induction and repression is important for analyzing drug reactions and toxicity by regulating metabolic pathways and hormone production.