Q.40 Which of the following is true about Poly(A) tail ?
(A). Synthesizes post transcriptionally
(B). Usually shorter than 300 nt
(C). Its function is to protect the mRNA from cytoplasmic RNAases
(D). Its function is to stimulate translation
Choose the correct answer from the options given below:
1. (A), (B) and (D) only.
2. (A), (B) and (C) only.
3. (A), (B), (C) and (D).
4. (B), (C) and (D) only.
The Poly(A) tail is a critical post-transcriptional modification on eukaryotic mRNA that enhances stability and translation efficiency. The correct answer is 3. (A), (B), (C) and (D).
Poly(A) Tail Overview
Poly(A) tails consist of 200-250 adenine nucleotides added to the 3′ end of pre-mRNA during processing, aiding export, stability, and protein synthesis.
Option Breakdown
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(A) Synthesizes post transcriptionally: Correct. Polyadenylation occurs after transcription via cleavage and poly(A) polymerase action on pre-mRNA.
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(B) Usually shorter than 300 nt: Correct. Typical lengths are ~250 nt in mammals, controlled by nuclear poly(A)-binding protein, shortening over time.
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(C) Its function is to protect the mRNA from cytoplasmic RNAases: Correct. It binds PABP, shielding the 3′ end from exonucleases and delaying degradation.
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(D) Its function is to stimulate translation: Correct. Poly(A)-PABP interaction forms a closed-loop mRNA structure, boosting initiation via eIF4G/eIF4E.
Why Option 3?
All statements accurately describe the synthesis, length, and dual roles (stability and translation) of the Poly(A) tail in mRNA lifecycle.
