Operons are genetic regulatory systems primarily found in prokaryotes. They consist of promoters, operators, and genes organized into one functional unit. The role of operons is to control the expression of genes in response to environmental conditions, allowing cells to adapt by regulating transcription. For example, the lac operon in E. coli allows the bacteria to utilize lactose when glucose is not available. This coordinated regulation enhances metabolic efficiency and contributes to cellular survival.