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Question #45235
The Question
In the context of cellular defense via RNA interference (RNAi), the transient nature of post-transcriptional gene silencing is biologically advantageous. Which structural feature of the RNA molecule directly ensures this rapid turnover by making the molecule inherently labile, and by what mechanism?
Options
- A.
The presence of uracil instead of thymine, which prevents DNA ligase from permanently integrating siRNA into the host genome.
- B.
The presence of a 2'-OH group on the ribose sugar, which acts as a nucleophile to facilitate autocatalytic cleavage of the phosphodiester backbone.
- C.
The single-stranded nature of the mRNA target, which exposes its hydrogen bonds to rapid enzymatic degradation by restriction endonucleases.
- D.
The absence of a 3'-OH group on the siRNA, which prevents the extension of the silencing complex by RNA-dependent RNA polymerase.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
RNAi|siRNA|Ribonuclease|Hydrolysis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the NCERT line that 'RNA is unstable due to the 2'-OH group' but fail to connect this chemical lability to its physiological advantage in regulatory mechanisms like RNAi.
The trap involves confusing the evolutionary reason for Uracil vs Thymine (mutation repair) with the Ribose vs Deoxyribose difference (backbone stability and hydrolysis).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biomolecules - Class 11 |
| Concept | Nucleic Acid Structural Stability |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |