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Question #133127
The Question
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): In blue-white screening, bacterial colonies containing the recombinant plasmid appear white when grown on an agar medium containing ampicillin and a chromogenic substrate. Reason (R): The insertion of foreign DNA into the coding sequence of the ampicillin resistance gene causes insertional inactivation, preventing the enzymatic cleavage of the chromogenic substrate.
In the light of the above statements, choose the most appropriate answer from the options given below:
Options
- A.
Both (A) and (R) are correct and (R) is the correct explanation of (A)
- B.
Both (A) and (R) are correct but (R) is not the correct explanation of (A)
- C.
(A) is correct but (R) is not correct
- D.
(A) is not correct but (R) is correct
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
Selectable Marker vs Cloning Site|LacZ Gene|pBR322
Why This Question Is Tricky
Examiner Levers
Logical Assertion
Tests the causal relationship between two true statements.
Difficulty Boost : +4Common Mistakes
Conceptual Pivot: Students often conflate the two distinct selectable marker systems taught in NCERT (antibiotic resistance vs. chromogenic enzyme production).
The trap relies on failing to distinguish the specific location of the insertion.
For blue-white screening to work on an ampicillin plate, the ampicillin resistance gene must remain intact (to select transformants), while the beta-galactosidase gene must undergo insertional inactivation (to select recombinants).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Selectable Marker vs Cloning Site |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |