Final answer:
The lac repressor binds to the lacO site within the lac operon, which controls the transcription of genes involved in lactose metabolism.
Step-by-step explanation:
The lac operon is a segment of DNA that includes regulatory regions and structural genes, such as lacZ, lacY, and lacA, which are essential for lactose metabolism. When lactose is not present, the lac repressor, which is a product of the lacl gene, is bound to the operator region, designated as lacO, inhibiting RNA polymerase from transcribing the structural genes.
In the presence of lactose, allolactose is formed, which binds to the lac repressor, leading to its dissociation from the lacO site. This allows RNA polymerase to move past the operator to transcribe the genes required for lactose digestion. Furthermore, the operon is also regulated by cAMP levels which affect the binding of catabolite activator protein (CAP) to the promoter region, mediating the use of lactose in the absence of glucose.
The lac repressor binds to the lacO site within the lac operon. The lacO site is the operator region of the lac operon where the repressor protein binds to prevent transcription of the lacZ, lacY, and lacA genes.