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Question #47744
The Question
A recombinant plasmid carrying a therapeutic gene under the control of a wild-type lac promoter is introduced into competent E. coli cells. To rapidly scale up the biomass, the transformants are cultured in a bioreactor using a medium rich in glucose. Despite successful transformation and high cell density, the expression of the therapeutic protein is found to be negligible. What is the primary molecular mechanism responsible for this observation?
Options
- A.
High glucose levels induce the synthesis of the lac repressor, which binds to the operator and permanently blocks transcription.
- B.
Glucose metabolism lowers intracellular cAMP levels, preventing the formation of the CAP-cAMP complex required for efficient RNA polymerase binding.
- C.
The high metabolic load of the plasmid in a glucose-rich medium triggers the host cell to actively secrete the recombinant DNA.
- D.
Glucose acts as a corepressor by directly binding to the lac operator, physically obstructing the promoter region.
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
Plasmid_Vs_Chromosomal_DNA|Restriction_Enzymes|Elution
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the negative control of the lac operon (lactose binds repressor) but neglect the positive control mechanism (Catabolite Repression via glucose/cAMP).
The trap lies in assuming that successful transformation automatically equals gene expression, failing to recognize that biotechnological scale-up requires specific promoter-inducer environments.
Using glucose as a primary carbon source actively suppresses lac-promoter-driven transgenes.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Elution Process |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |