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Question #46482
The Question
A transgenic tobacco plant engineered for nematode resistance via RNA interference (RNAi) continuously produces dsRNA specific to a vital gene of Meloidogyne incognita. After several years of successful biocontrol, a resistant nematode population emerges. Genomic sequencing reveals absolutely no mutations in the target vital gene's sequence. Which of the following is the most scientifically plausible mechanism for this acquired resistance?
Options
- A.
The nematode secretes systemic proteases into the root nodule that degrade the plant's Argonaute (RISC) complex prior to feeding.
- B.
A structural mutation in the RNase III domain of the nematode's endogenous Dicer enzyme, preventing the cleavage of ingested dsRNA.
- C.
A gain-of-function mutation in the nematode's RNA-dependent RNA polymerase (RdRP), leading to hyper-amplification of siRNAs.
- D.
The nematode upregulates the expression of Agrobacterium-derived Ti plasmid promoters to suppress antisense RNA transcription.
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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
Co-evolutionary Resistance|RNA Interference (RNAi) Mechanism|Baculovirus Host Specificity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently harbor the misconception that the plant's enzymes actively destroy the nematode's mRNA.
In reality, the plant merely acts as a delivery vector for the dsRNA trigger.
The nematode's own endogenous machinery (Dicer and RISC) is hijacked to commit 'cellular suicide'.
Therefore, an evolutionary workaround for the pest is to mutate its own highly conserved RNAi processing enzymes (like Dicer), proving that anthropogenic biocontrol is still subject to co-evolutionary resistance.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Evolution - Class 12 |
| Concept | Co-evolutionary Resistance |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |