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Question #47718
The Question
During a recombinant DNA experiment using the pUC18 vector and an E. coli host, a student performs blue-white screening on an agar plate containing Ampicillin and X-gal. Surprisingly, the control plate containing E. coli transformed strictly with non-recombinant (empty) pUC18 vectors yields exclusively white colonies. Which of the following is the most scientifically accurate explanation for this anomaly?
Options
- A.
The host E. coli strain has a complete deletion of the lacZ gene rather than the specific ΔM15 mutation, preventing α-complementation.
- B.
The host E. coli strain possesses a wild-type lacZ gene, leading to the independent synthesis of functional β-galactosidase.
- C.
The non-recombinant pUC18 vector experienced a spontaneous frameshift mutation in the ampR gene during transformation.
- D.
The X-gal in the medium was competitively inhibited by the presence of an inducer like IPTG.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Baculovirus|Autographa californica|Chromosomal DNA
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often rote-memorize 'White = Recombinant, Blue = Non-recombinant' (Insertional Inactivation) without understanding the bipartite nature of the β-galactosidase enzyme in this system.
This question tests the 'NCERT-Plus' concept of α-complementation, highlighting that the host cell is not a passive vessel but must actively provide the ω-fragment for the blue color to appear.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Plasmid vs Chromosomal DNA |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |