Q.38 Match the classes of RNA molecules in Group I with their functions in Group II.
Group I Group II
P. snoRNA 1. Protects germline from transposable elements
Q. piRNA 2. Blocks translation of selected mRNA
R. miRNA 3. Template for telomere elongation
S. snRNA 4. Modification and processing of rRNA
5. Splicing of RNA transcripts
(A) P-3, Q-5, R-2, S-4 (B) P-1, Q-3, R-2, S-5
(C) P-1, Q-4, R-5, S-2 (D) P-4, Q-1, R-2, S-5
SnoRNA guides rRNA modifications, piRNA silences transposable elements, miRNA represses mRNA translation, and snRNA drives splicing. The correct match is option (D) P-4, Q-1, R-2, S-5.
Correct Answer
Option (D) pairs each RNA class accurately: P (snoRNA) with 4 (modification and processing of rRNA), Q (piRNA) with 1 (protects germline from transposable elements), R (miRNA) with 2 (blocks translation of selected mRNA), and S (snRNA) with 5 (splicing of RNA transcripts). SnoRNAs (C/D box and H/ACA box types) direct 2′-O-methylation and pseudouridylation on rRNA during ribosome biogenesis. PiRNAs form complexes with PIWI proteins to suppress transposons in gonads, preventing genome instability.
Group I Functions
-
P. snoRNA: Primarily modifies rRNA via chemical changes like methylation and pseudouridylation in the nucleolus; also aids rRNA processing.
-
Q. piRNA: Targets transposons in germline cells through PIWI-piRNA pathway, cleaving or silencing them to safeguard DNA.
-
R. miRNA: Binds mRNA 3′ UTRs in RISC complex, inhibiting translation or promoting decay of target transcripts.
-
S. snRNA: Core spliceosome components (U1, U2, U4, U5, U6) catalyze intron removal from pre-mRNA.
Option Breakdowns
| Option | Matches | Correct? | Why Valid/Invalid |
|---|---|---|---|
| (A) P-3, Q-5, R-2, S-4 | snoRNA-telomere; piRNA-splicing; miRNA-translation block; snRNA-rRNA mod | No | SnoRNA does rRNA mod (4), not telomeres (TERC does 3); snRNA splices (5), not rRNA mod. |
| (B) P-1, Q-3, R-2, S-5 | snoRNA-transposons; piRNA-telomere; miRNA-translation block; snRNA-splicing | No | PiRNA protects from transposons (1), not telomeres; snoRNA unrelated to transposons. |
| (C) P-1, Q-4, R-5, S-2 | snoRNA-transposons; piRNA-rRNA mod; miRNA-splicing; snRNA-translation block | No | MiRNA blocks translation (2), not splicing; piRNA unrelated to rRNA. |
| (D) P-4, Q-1, R-2, S-5 | snoRNA-rRNA mod; piRNA-transposons; miRNA-translation block; snRNA-splicing | Yes | All align with established roles in RNA biology. |
Exam Relevance
This matching tests non-coding RNA roles in gene regulation and RNA processing, key for molecular biology exams. Focus on distinctions: snoRNA (ribosome-focused), piRNA (genome defense), miRNA (post-transcriptional silencing), snRNA (splicing machinery). Review pathways like RISC for miRNA and spliceosome for snRNA to ace similar questions.
