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Question #46409
The Question
A biotechnologist engineers a transgenic strain of bacteria where the native promoter of the cryIAc gene is replaced by a wild-type lac operon promoter. These bacteria are cultured in a bioreactor containing a medium rich in both glucose and lactose. The harvested bacteria are then fed to susceptible cotton bollworm larvae. Which of the following accurately describes the fate of the larvae and the underlying molecular mechanism?
Options
- A.
The larvae will die because lactose induces the removal of the repressor protein, leading to protoxin synthesis which is then activated by the alkaline gut.
- B.
The larvae will survive because high glucose causes catabolite repression, preventing cryIAc transcription so no protoxin is available for the alkaline gut to activate.
- C.
The larvae will die because glucose accelerates bacterial metabolism, producing excess protoxin that is subsequently activated by the acidic pH of the insect gut.
- D.
The larvae will survive because while lactose induces protoxin synthesis, the residual glucose acts as a competitive inhibitor for the activated toxin receptors in the midgut.
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
Glucose Repression|Bt Toxin Activation Trigger|Alkaline Gut pH
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'Lactose = Inducer = Operon ON' and 'Alkaline gut = Toxin ON' in isolation.
This question tests the hierarchical nature of gene regulation (Glucose preference overrides Lactose induction) and sequential dependency (Transcriptional synthesis must occur before post-translational activation).
The trap is failing to recognize that the secondary checkpoint (alkaline gut) is irrelevant if the primary checkpoint (glucose repression) halts synthesis.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Glucose Repression |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |