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Question #47723
The Question
A researcher modifies a pBR322 vector, inadvertently causing a mutation in the regulatory sequence of the 'ori' region that alters its stringency, thereby favoring runaway (uncontrolled) plasmid replication. Concurrently, a large eukaryotic gene is successfully inserted at the Sal I restriction site. If E. coli cells transformed with this recombinant plasmid are cultured, which of the following represents the most likely physiological and genetic outcome?
Options
- A.
The host cells will experience severe metabolic exhaustion due to the continuous drain on replication machinery, and will fail to survive in a Tetracycline-containing medium.
- B.
The host cells will fail to initiate plasmid replication because altered ori stringency prevents the binding of DNA polymerase, leading to Ampicillin susceptibility.
- C.
The runaway replication will amplify the disrupted Tet^R gene, restoring Tetracycline resistance through a compensatory high copy number.
- D.
The metabolic load will trigger the host cell to selectively degrade the recombinant plasmids, resulting in the loss of both Ampicillin and Tetracycline resistance.
Check Your Answer
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
Lac_Operon_Inducibility|Beta-galactosidase|X-gal
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often fail to link the molecular mechanism of insertional inactivation (structural disruption of a reading frame) with the physiological consequences of plasmid copy number.
A common misconception is that a massive increase in copy number (runaway replication) might compensate for a weakened or disrupted gene, or they fail to recognize that uncontrolled replication is highly detrimental (metabolic burden) rather than beneficial to the host cell.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Blue-White Screening Mechanism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |