Explain how this repressible operon can be turned off. Figure 18.3(b) in the text will help.
a. The repressible operon can be turned off by an excess of the end product of the pathway, which acts as a corepressor to bind to the repressor protein and activate it to bind to the operator, thereby blocking transcription.
b. It can also be turned off by the buildup of a corepressor that activates the repressor protein to bind to the operator and block transcription.
c. Another way to turn off the repressible operon is through the binding of the inducer molecule to the repressor protein, causing it to release from the operator and allowing transcription to occur.
d. Finally, the repressible operon can be turned off by the absence of the inducer molecule, which allows the repressor protein to bind to the operator and block transcription.