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Question #45903
The Question
A population of cotton bollworms (Helicoverpa armigera) exhibits complete resistance to Bt cotton expressing the cryIAc gene. Laboratory analysis confirms that the alkaline pH of the insect's midgut and the proteolytic cleavage of the inactive protoxin into the active toxin are occurring normally. Which of the following molecular events in the insect is the most probable cause of this resistance?
Options
- A.
A genetic mutation altering the mRNA codons for the midgut epithelial receptors, changing their primary polypeptide sequence and preventing toxin binding.
- B.
A loss of fidelity in the insect's aminoacyl-tRNA synthetase, leading to the erroneous translation and misfolding of the ingested Cry protoxin.
- C.
Activation of RNA interference (RNAi) within the insect's gut cells, which silences the cryIAc mRNA before it can be translated into the active toxin.
- D.
An alteration in the insect's gut flora that secretes enzymes to degrade the active toxin before it can undergo translation by the insect's ribosomes.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Cry toxin|Alkaline pH|Protoxin Activation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently confuse 'who' is performing translation in transgenic applications.
In Bt crops, the plant transcribes and translates the cry gene into a protoxin; the insect merely ingests the protein.
The trap options (B, C, D) exploit this by suggesting the insect's translational machinery acts on the cry gene or mRNA.
True resistance in this scenario must stem from modifications to the insect's own endogenous proteins (the midgut receptors) that interact with the toxin.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | tRNA Charging Accuracy |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |