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Question #45857
The Question
A researcher is standardizing a PCR protocol to amplify a gene from a viral DNA sample that exhibits a base composition of 20% Adenine, 30% Thymine, 15% Guanine, and 35% Cytosine. Which of the following statements is INCORRECT regarding the thermodynamic properties and amplification dynamics of this specific sample?
Options
- A.
The native genetic material is single-stranded, hence it inherently violates Chargaff's rule of base equivalence.
- B.
The initial denaturation step at 94°C in the very first PCR cycle is essential to break the hydrogen bonds between the two complementary genomic strands.
- C.
Primers designed to anneal to regions with high local Cytosine content will require a higher annealing temperature (Tm) due to triple hydrogen bonding.
- D.
Following the first complete extension step by Taq polymerase, the newly synthesized double-stranded DNA molecules will obey Chargaff's rule.
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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_Thermal_Stability|Chargaff’s_Rule_Limitation|DNA_Melting
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students mechanically associate the first step of PCR (Denaturation at 94°C) with the separation of two DNA strands.
However, if the base composition violates Chargaff's rule, the template is ssDNA.
Therefore, the first cycle's denaturation step cannot be for separating two complementary strands.
This tests the student's ability to synthesize molecular structure (Chargaff's rule) with biotechnological processes (PCR thermal dynamics).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Chargaff’s Rule Limitation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |