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Question #47752
The Question
During PCR primer design, a student intends to amplify a specific target gene. Instead of designing a forward primer complementary to the 3' end of the template (non-coding) strand, the student mistakenly designs a primer that is exactly complementary to the 5' end of the coding strand. Which of the following best explains the molecular consequence of this error during the PCR cycles?
Options
- A.
The primer will fail to anneal because the coding strand lacks the necessary promoter region for Taq polymerase binding.
- B.
The primer will anneal, but extension will attempt to occur in the 3' to 5' direction, which Taq polymerase cannot catalyze.
- C.
The primer will anneal to the coding strand, but its free 3'-OH group will be oriented away from the target gene sequence, preventing amplification.
- D.
The primer will not anneal because DNA primers can only form hydrogen bonds with the non-coding (template) strand.
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
Taq Polymerase Thermal Stability|Heat Shock Thermal Gradient|PCR Denaturation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Mastery of antiparallel DNA geometry and the physical orientation of the 3'-OH group.
A common misconception is memorizing 'primers bind to DNA' without visualizing that the 3'-OH must physically point towards the sequence to be amplified.
Students often confuse the inability to amplify with a failure of Taq polymerase to bind, or mistakenly believe Taq will attempt 3' to 5' synthesis.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biotechnology : Principles and Processes - Class 12 |
| Concept | Heat Shock Thermal Gradient |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |