For a repressible operon to be transcribed, which of the following must occur?
A) A corepressor must be present.
B) RNA polymerase and the active repressor must be present.
C) RNA polymerase must bind to the promoter, and the repressor must be inactive.
D) RNA polymerase cannot be present, and the repressor must be inactive.
E) RNA polymerase must not occupy the promoter, and the repressor must be inactive.

Question

Quizplus · Accepted Answer

In a repressible operon, the repressor is normally bound to the operator, preventing RNA polymerase from binding to the promoter and transcribing the genes. However, if the substrate for the pathway controlled by the operon is present, it can bind to the repressor, causing a change in its conformation that allows it to no longer bind to the operator. This allows RNA polymerase to bind to the promoter and transcribe the genes. Therefore, for a repressible operon to be transcribed, RNA polymerase must bind to the promoter, and the repressor must be inactive.

For a Repressible Operon to Be Transcribed, Which of the Following