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Question #47490
The Question
A plant pathologist attempts to amplify the genetic material of the causative agent of Potato Spindle Tuber disease using a standard Polymerase Chain Reaction (PCR) with Taq polymerase, primers, and dNTPs. The amplification completely fails. Which of the following best explains the primary molecular reason for this failure?
Options
- A.
The pathogen consists of free, low molecular weight dsRNA, which requires an RNA-dependent RNA polymerase instead of Taq polymerase.
- B.
The pathogen lacks a protein coat and its genome is free ssRNA, requiring prior conversion to cDNA because Taq polymerase is strictly a DNA-dependent DNA polymerase.
- C.
The absence of a protective capsid causes the pathogen's naked DNA genome to rapidly degrade during the 94°C denaturation step of PCR.
- D.
Taq polymerase is an RNA-dependent DNA polymerase that fails to amplify the viroid genome due to the absence of a viral-encoded primer.
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
Household_Product_Fermentation|Aspergillus_niger|Metabolic_Pathway
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that PCR amplifies 'genetic material' and that viroids are 'infectious genetic material'.
The trap is failing to integrate the specific biochemical nature of the viroid genome (ssRNA) with the strict substrate specificity of Taq polymerase (DNA-dependent DNA polymerase).
Standard PCR always fails on RNA genomes without a prior reverse transcription step.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biological Classification - Class 11 |
| Concept | Deuteromycetes 'Fungi Imperfecti' |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |