Question

Which one of the following conditions leads to an approximately 50-fold increase in RNA transcription of the lac operon? (CRP stands for cyclic AMP [cAMP] receptor protein)

• A. Q and S
• B. P and R
• C. P and S
• D. Q and R

Hint:

CRP-cAMP binding increases RNA polymerase binding, and the lack of repressor binding is crucial for enhanced transcription in the lac operon.

Answer 1

The Correct Option is C

Step 1: Understanding the Lac Operon.
The lac operon is a system that regulates the metabolism of lactose in bacteria. Transcription of this operon is influenced by the binding of cyclic AMP receptor protein (CRP) and the lac repressor.
Step 2: Mechanism of Increased Transcription.
- Q: Binding of CRP-cAMP complex to a site near the lac promoter facilitates RNA polymerase binding and enhances transcription. - S: Lac repressor not bound to the lac operator allows for the transcription process to occur.
Step 3: Conclusion.
For the transcription to be maximally increased, both the CRP-cAMP binding (P) and the absence of the lac repressor (S) must occur. Thus, the correct answer is (C) P and S.