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Question #45127
The Question
A transgenic tobacco plant was developed using Agrobacterium vectors to express nematode-specific dsRNA, conferring resistance against Meloidogyne incognita via RNA interference (RNAi). After several years of successful cultivation, a new strain of the nematode is found to heavily infest these transgenic plants. Assuming the plant still expresses the dsRNA optimally, which of the following is the most likely evolutionary mechanism for the nematode's acquired resistance?
Options
- A.
A point mutation in the nematode's target gene altered the mRNA transcript, abolishing the perfect complementarity required for siRNA-mediated cleavage.
- B.
The nematode evolved to secrete endonucleases that specifically degrade the T-DNA integrated into the host plant's nuclear genome.
- C.
The nematode developed a mutation that prevents the absorption of host-derived single-stranded sense RNA into its gut cells.
- D.
The nematode's cells upregulated the expression of the Dicer enzyme, leading to the rapid degradation of the plant-derived dsRNA before RISC assembly.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
RNAi|Meloidogyne incognita|Host plant|Vector-mediated transformation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'dsRNA causes silencing' without internalizing the exact mechanism—that silencing is strictly sequence-dependent via complementary base pairing.
The trap in Option D exploits a common misconception regarding enzymes: students know Dicer is an RNase that cleaves dsRNA, so they mistakenly assume its upregulation would 'destroy the threat', forgetting that Dicer's cleavage is exactly what creates the active siRNA weapon.
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 |