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Question #45900
The Question
A researcher designs degenerate primers to amplify a specific gene based on its known amino acid sequence, accounting for codon degeneracy. After performing PCR using standard Taq polymerase, gel electrophoresis reveals multiple non-specific amplicons alongside the target band. Which of the following intrinsic properties of Taq polymerase primarily explains why it exacerbates this non-specific amplification?
Options
- A.
Taq polymerase possesses robust 3' → 5' exonuclease activity, which degrades mismatched primers and creates new, non-specific initiation sites.
- B.
Taq polymerase lacks 3' → 5' proofreading activity, allowing it to efficiently extend primers even if the 3' terminal nucleotide is mismatched with the template.
- C.
Taq polymerase dictates a lower annealing temperature for the reaction, which inherently decreases the stringency of primer binding across the genome.
- D.
Taq polymerase exhibits high fidelity and strictly requires perfect Watson-Crick base pairing at the wobble position to initiate the extension phase.
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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
Taq Polymerase Thermal Stability|Genetic Code Degeneracy|PCR
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize Taq polymerase's thermal stability (denaturation survival) but overlook its functional limitation (lack of 3' → 5' proofreading).
This question tests the synthesis of 'codon degeneracy' (which necessitates degenerate primers) with the 'error-prone nature of Taq' (which readily extends mismatched 3' ends), bridging basic molecular biology with applied biotechnology.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Genetic Code Degeneracy |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |