(a)Components Repressor Promoter Operator Leader Structural genes gene(7) (P) gene(O) 口乳糖操纵子 Operator. binding site Repressor RNA protein polymerase The components Lactose. binding site Lactose of the wild-type (b)IOZ rA(wild type)-No lactose present-Repressed Lac operon and Repressor binds to operator, lo transcription the response in blocking transcription Q No enzymes the absence and (c)IOZY A(wild type)-Lactose present-Induced the presence of P lactose, No binding occurs; Transcription transcription proceeds Q Operator-binding site is altered when bound to lactose mRNA Translation Enzymes□ 乳糖操纵子 The components of the wild-type lac operon and the response in the absence and the presence of lactose