An operon is a cluster of genes that are regulated together, allowing for coordinated expression in prokaryotic cells, such as bacteria. It typically consists of a promoter, an operator, and one or more structural genes. The promoter is where RNA polymerase binds to initiate transcription, while the operator acts as a regulatory switch that can be turned on or off by specific proteins. Operons enable cells to efficiently manage resources by controlling the production of proteins based on environmental needs. A well-known example is the lac operon, which regulates the metabolism of lactose in E. coli. When lactose is present, the operon is activated, allowing the bacteria to utilize it as an energy source.