Before You Begin
Question #47747
The Question
A researcher attempts to transform a competent psychrophilic bacterium (optimal growth at 10°C) with a recombinant plasmid using the standard E. coli protocol. The cells are treated with divalent cations (Ca2+) on ice, followed by a brief heat shock at 42°C, and then returned to ice. The experiment yields no transformants, and spectrophotometric analysis reveals massive cell lysis. Which of the following best explains this observation?
Options
- A.
The 42°C heat shock induces hyper-fluidity and loss of membrane integrity due to a high concentration of unsaturated fatty acids in the psychrophile's cell membrane.
- B.
The divalent cations fail to create transient pores because psychrophilic membranes are exclusively composed of saturated branched-chain lipids.
- C.
The sudden shift to 42°C denatures the double-stranded plasmid DNA, rendering it incapable of autonomous replication within the host.
- D.
Psychrophiles lack the specific ori-recognizing proteins required to initiate replication of mesophilic plasmids, leading to cellular apoptosis.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Competent_Cell_Preparation|Blue-White_Screening_Mechanism|Restriction_Endonuclease_Nomenclature
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize the '42°C heat shock' as a universal biological constant for all transformations, failing to realize it is specifically calibrated for the membrane melting temperature of mesophiles like E. coli.
This question tests the synthesis of Biotechnology protocols with the ecological concept of homeoviscous adaptation (lipid saturation vs. environmental temperature).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Competent Cell Preparation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |