Induced(derepressed)lac operon Promoter Structural Operator lacz lacy lacA genes regulatory sites in transcription operon AUG UAA AUG UAA AUG UAA Polycistronic translation mRNA β- galactosidase lactose β- galactoside permease transacetylaseInduced (derepressed) lac operon lacZ lacY lacA AUG UAA AUG UAA AUG UAA Structural genes & regulatory sites in operon Polycistronic mRNA -galactosidase lactose permease -galactoside transacetylase transcription translation Promoter Operator