Question

Assertion (A): The transcripts of RNA polymerases I and III are not processed. Reason (R): RNA polymerases I and III lack a C-terminal domain (CTD).

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

All RNA is “processed” (cleaned up), but only Pol II has the CTD “tail” to handle mRNA-specific tasks.

Answer 1

The Correct Option is D

Step 1: Concept
RNA processing (capping, splicing, tailing) is standard for mRNA.

Step 2: Meaning
Pol I handles rRNA, Pol II handles mRNA, Pol III handles tRNA.

Step 3: Analysis
Assertion (A) is incorrect: while they do not get a $5'$ cap or poly-A tail, transcripts of Pol I (rRNA) and Pol III (tRNA) are extensively processed via cleavage and chemical modifications. Reason (R) is correct; only RNA Pol II has the long CTD that recruits processing enzymes for mRNA.

Step 4: Conclusion
The assertion is false, but the reason is scientifically accurate.

Final Answer: (D)