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Question #47719
The Question
A researcher utilizes a theoretical hybrid cloning vector containing ampR, tetR, and lacZ' (beta-galactosidase alpha-peptide) genes. The BamHI restriction site is located exclusively within the tetR gene. After ligating a foreign DNA fragment at the BamHI site, the transformed E. coli cells are plated directly onto an agar medium containing Ampicillin, Tetracycline, and X-gal. Which of the following correctly describes the outcome for the true recombinants?
Options
- A.
They will form white colonies because insertion at the BamHI site simultaneously inactivates both the tetR and lacZ' genes.
- B.
They will form blue colonies because the lacZ' gene remains intact and the ampR gene ensures survival on the medium.
- C.
They will fail to form colonies because insertional inactivation of the tetR gene renders them sensitive to Tetracycline, causing cell death.
- D.
They will form colorless colonies because the presence of dual antibiotics represses the expression of the intact lacZ' gene.
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
pBR322|AmpR|TetR|Restriction Endonuclease Nomenclature
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize independent facts ('BamHI insertion = recombinant' and 'intact lacZ = blue colony') without synthesizing the physiological reality of the selective medium.
The trap relies on the student failing to recognize that antibiotic sensitivity (cell death) is a binary, overriding event that precedes any colorimetric reporter assay.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | pBR322 Selection Logic |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |