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Question #47579
The Question
During the in vitro amplification of a gene of interest via PCR, the rapid accumulation of amplicons mimics a high 'molecular mitotic index'. However, the thermal kinetics and enzymatic properties of Taq polymerase introduce specific constraints. Which of the following statements regarding this process is INCORRECT?
Options
- A.
Taq polymerase remains catalytically active during the 94°C denaturation phase, eliminating the need to add fresh enzyme after every thermal cycle.
- B.
To maintain high sequence fidelity during rapid synthesis, Taq polymerase utilizes a 5' → 3' exonuclease activity to proofread and excise mismatched nucleotides.
- C.
The theoretical exponential yield (2^n) of amplicons eventually plateaus due to dNTP depletion, primer exhaustion, and the finite thermal half-life of the enzyme.
- D.
If the annealing temperature drops significantly below the primer's melting temperature (Tm), Taq polymerase may extend non-specifically bound primers, reducing amplicon purity.
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
Taq Polymerase|PCR|Denaturation-Annealing-Extension
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Directionality of Exonuclease Activity and Enzyme Fidelity.
Students often memorize that polymerases possess 'exonuclease activity' but fail to distinguish between 5' → 3' (primer removal/nick translation) and 3' → 5' (proofreading).
Additionally, there is a common misconception that Taq polymerase has absolute fidelity because it is used in precise biotechnological applications, whereas it actually lacks proofreading capabilities entirely.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Cell Cycle and Cell Division - Class 11 |
| Concept | Mitotic Index Implications |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |