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Question #47633
The Question
In a eukaryotic cell infected by a virus, the RNA interference (RNAi) pathway acts as a primary cellular defense. During a severe infection, despite the presence of abundant complementary dsRNA and structurally normal RISC (RNA-induced silencing complex), uncontrolled viral replication occurs. Applying the concept of limiting factors to this post-transcriptional gene silencing mechanism, which of the following is the most scientifically accurate explanation for the failure of host immunity?
Options
- A.
RNAi is a pre-transcriptional mechanism; hence, it cannot degrade viral mRNA once it reaches the cytoplasm.
- B.
The viral mRNA transcription rate exceeds the V_max of the host's Dicer and RISC enzymes, rendering the silencing machinery kinetically saturated.
- C.
The complementary dsRNA binds to the viral mRNA, but the absence of host reverse transcriptase prevents the degradation of the duplex.
- D.
The virus utilizes host RNA polymerase I to synthesize its mRNA, which is inherently resistant to RISC-mediated cleavage.
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
RISC_Complex|dsRNA|Dicer|Agrobacterium_Tumefaciens
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often view genetic defense mechanisms like RNAi as absolute 'on/off' switches.
This question requires synthesizing concepts from Biotechnology (RNAi) with Biomolecules/Plant Physiology (Enzyme Kinetics and Limiting Factors).
The trap is failing to recognize that a fully functional, non-mutated defense system can still fail if it is kinetically overwhelmed by substrate saturation.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Photosynthesis in Higher Plants - Class 11 |
| Concept | Law of Limiting Factors |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |