AP BIOLOGY

Detailed explanation-1: -The lac operon consists of three coding regions in tandem, lacZ, lacY, and lacA. The lacZ gene encodes -galactosidase, which degrades lactose. The lacY gene product, lactose permease, transports lactose into the cell, and the lacA gene product, lactose acetylase, has an unknown and not usually necessary function.

Detailed explanation-2: -Final answer: Enhancer is not a part of an operon.

Detailed explanation-3: -Structure of the lac operon. The DNA of the lac operon contains (in order from left to right): CAP binding site, promoter (RNA polymerase binding site), operator (which overlaps with promoter), lacZ gene, lacY gene, and lacA gene.

Detailed explanation-4: -CAP binds with cAMP, and the CAP-cAMP complex then binds to a specific DNA sequence found upstream of the lac operon operator and promoter. CAP-cAMP complex binding leads to enhanced RNA polymerase binding and activation of gene expression from the lac operon.