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Question #45875
The Question
A researcher uses standard Taq polymerase to amplify a 2 kb human gene for recombinant protein expression. Upon sequencing the cloned product, multiple point mutations are detected that were absent in the original template. In contrast, in vivo replication of the same sequence in E. coli shows extremely high fidelity. What is the primary biochemical reason for this discrepancy?
Options
- A.
Taq polymerase lacks 5' → 3' exonuclease activity, which is essential for proofreading newly synthesized DNA.
- B.
Taq polymerase lacks 3' → 5' exonuclease activity, preventing the excision of mismatched nucleotides during extension.
- C.
The high temperature (72°C) during the extension phase denatures the proofreading domain of Taq polymerase.
- D.
Taq polymerase synthesizes DNA in short Okazaki fragments that are highly prone to ligation errors during PCR.
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
DNA Polymerase Directionality|Taq Polymerase Thermal Stability|PCR
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between the directionality of polymerization (5' → 3') and proofreading (3' → 5').
The trap relies on the common misconception that Taq polymerase, being a staple of modern biotechnology, possesses all the high-fidelity features of standard in vivo polymerases.
Students must synthesize knowledge from 'Molecular Basis of Inheritance' (proofreading directionality) with 'Biotechnology: Principles and Processes' (properties of Taq polymerase).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | DNA Polymerase Directionality |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |