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Question #47724
The Question
The initiation of DNA replication in E. coli is highly stringent, relying on the specific recognition of the ori sequence by initiator proteins. In contrast, PCR utilizes synthetic primers whose binding is purely thermodynamically driven. If the annealing temperature in a PCR cycle is set significantly lower than the primer's calculated melting temperature (Tm), what is the primary consequence, and why does natural replication not suffer from this specific kinetic error?
Options
- A.
Non-specific amplification occurs due to mismatched primer annealing; natural replication avoids this as initiation strictly requires specific initiator protein binding at the ori site.
- B.
Amplification fails completely as primers cannot anneal to the template; natural replication avoids this because RNA primase synthesizes primers directly on the unwound DNA.
- C.
Taq polymerase introduces extensive point mutations due to altered kinetics; natural replication avoids this because DNA polymerase III possesses 3' to 5' exonuclease activity.
- D.
Primers bind exclusively to the ori sequence of the template DNA; natural replication avoids this because helicase unwinds DNA only at specific recognition sites.
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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
Selectable_Marker_vs_Cloning_Site|pBR322|Ampicillin_Tetracycline
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the thermodynamic stringency of PCR with the enzymatic/protein-driven stringency of natural replication.
A common misconception is that lowering the annealing temperature in PCR prevents primer binding (thinking 'lower energy = no reaction'), whereas it actually permits promiscuous, non-specific binding due to reduced kinetic barriers for mismatched base pairing.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Blue-White Screening Mechanism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |