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Question #47730
The Question
During a cloning experiment, a researcher uses a plasmid vector containing an ampicillin resistance gene and a lacZ gene. After transformation into E. coli and plating on a medium with ampicillin and X-gal, both blue and white colonies appear. Plasmids are isolated from a blue colony (Plasmid X) and a white colony (Plasmid Y), linearized using a restriction enzyme that cuts only the vector backbone, and subjected to agarose gel electrophoresis. Which of the following statements correctly correlates their electrophoretic migration with their biochemical properties?
Options
- A.
Plasmid Y will migrate closer to the anode than Plasmid X because the insertion of foreign DNA alters its charge-to-mass ratio.
- B.
Plasmid X will migrate further from the well than Plasmid Y, and its host cells possess an intact enzyme capable of cleaving the chromogenic substrate.
- C.
Plasmid Y will migrate slower than Plasmid X, and its host cells produce blue colonies due to the synthesis of a truncated beta-galactosidase.
- D.
Plasmid X will migrate closer to the well than Plasmid Y because the absence of the insert allows it to maintain a larger hydrodynamic radius.
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
Agrobacterium_Tumefaciens_Mechanism|RNA_Interference_Mechanism|Ori_Sequence_Stringency
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize 'insertional inactivation' as a loss of function and subconsciously associate 'loss' with a smaller physical size.
The trap requires synthesizing two distinct NCERT concepts: (1) Insertional inactivation means DNA was ADDED (making the recombinant plasmid larger), and (2) Larger DNA fragments migrate slower/less distance in agarose gel electrophoresis.
Option B correctly links the smaller size of the non-recombinant plasmid with its faster migration and intact enzymatic activity.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Ori Sequence Stringency |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |