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Question #45128
The Question
RNA interference (RNAi) acts as a cellular defense mechanism in all eukaryotes. During an infection by a novel RNA virus that replicates via a double-stranded RNA (dsRNA) intermediate, a host cell mounts a robust RNAi response. However, the host cell unexpectedly suffers severe toxicity due to the sudden silencing of its own essential housekeeping gene, despite the virus producing no direct toxins. Which of the following is the most scientifically accurate explanation for this event?
Options
- A.
The viral dsRNA integrates into the host genome, causing insertional inactivation of the housekeeping gene.
- B.
The host's Dicer enzyme cleaves the viral dsRNA into siRNAs that inadvertently possess sequence complementarity to the host's housekeeping mRNA, triggering RISC-mediated degradation.
- C.
The viral dsRNA binds directly to the host's ribosomes, competitively inhibiting the translation of the housekeeping mRNA.
- D.
The host's RNA-dependent RNA polymerase (RdRP) mistakenly amplifies the host's own mRNA into dsRNA, which is then recognized as foreign and destroyed.
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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|Viral dsRNA|RISC|Host mRNA expression
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize RNAi strictly as a 'perfect defense mechanism against parasites/viruses' (like Meloidogyne incognita in NCERT) without realizing that the RISC complex is purely sequence-dependent, not origin-dependent.
The trap tests the understanding of 'off-target effects'—if a foreign dsRNA shares sequence homology with an endogenous host gene, the host's own defense system will inadvertently silence its own survival genes.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology and Its Applications - Class 12 |
| Concept | RNA Interference (RNAi) Mechanism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |