Question

Which of the following statement(s) is/are true:
(A). RNA polymerase lacks nuclease activity.
(B). The error rate of RNA synthesis much higher than DNA synthesis.
Choose the correct answer from the options given below:

• A. (A) only.
• B. (B) only.
• C. Both (A) and (B).
• D. Neither (A) nor (B).

Hint:

DNA replication requires high fidelity because errors become permanent mutations, whereas transcription mistakes are temporary and do not alter the genome of the cell.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Transcription (RNA synthesis) and replication (DNA synthesis) differ in their enzymatic mechanics, proofreading capabilities, and fidelity.

Step 2: Detailed Explanation:
- Statement (A) is true: Unlike DNA polymerases, RNA polymerases generally lack a highly efficient $3'\rightarrow5'$ proofreading exonuclease activity.
Although some RNA polymerases have minor backtracking nuclease capabilities, they do not possess a dedicated active site for proofreading.
- Statement (B) is true: Because RNA polymerase lacks rigorous proofreading activity, the error rate of transcription ($10^{-4}$ to $10^{-5}$) is several orders of magnitude higher than that of DNA replication ($10^{-9}$).
- This high error rate is biologically tolerated because transient, aberrant transcripts are rapidly degraded and do not permanently alter the genetic code.

Step 3: Final Answer:
Both statements are correct.