Labels:text | font | screenshot | black and white | white OCR: Wild-type 2. co/f express the genes encoding enzymes that metabolize lactose only when this sugar is present. As illustrated, in the absence of lactose, the lac repressor protein binds to the lac operator and prevents RNA polymerase from accessing the promoter. Thus, transcription of the lac operon is repressed. This type of control of gene expression is an example of negative regulation. Expression of the lac operon is in duced by lactose, which binds to the repressor and inactivates it. With the operator unoccupied because of the repressor's inability to bind to it, RNA polymerase can bind to the promoter to initiate transcription
