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Question #47741
The Question
During a cloning experiment using a plasmid vector, a researcher transforms competent E. coli cells and plates them on an agar medium containing Ampicillin and the chromogenic substrate X-gal. After incubation, the researcher observes a vast majority of blue colonies. Which of the following statements correctly deduces the molecular event and the nature of these colonies?
Options
- A.
The vector underwent self-ligation without the alien DNA, leaving the lacZ gene intact; the colonies are transformants but non-recombinants.
- B.
The alien DNA was successfully inserted into the lacZ gene, leading to its insertional inactivation; the colonies are recombinant transformants.
- C.
The competent cells failed to take up the plasmid but metabolized X-gal using endogenous enzymes; the colonies are non-transformants.
- D.
The vector's Ampicillin resistance gene was insertionally inactivated by the alien DNA, allowing the lacZ gene to overexpress; the colonies are recombinant non-transformants.
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
Agarose_Gel_Electrophoresis|DNA_Fragment_Size|Ethidium_Bromide
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between 'Transformation' (uptake of any plasmid) and 'Recombination' (uptake of a plasmid containing the alien insert).
Common Misconception: Students often intuitively associate a visible color change (blue) with a 'positive' or 'successful' experimental outcome (recombination).
In Blue-White screening, the logic is inverted: the 'loss' of color (white colonies) indicates successful recombination due to the insertional inactivation of the marker gene.
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 |