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Question #46478
The Question
During the post-industrialization period in England, the dark-winged melanic form of Biston betularia became abundant due to directional selection. Suppose a targeted RNA interference (RNAi) vector is introduced into a population of homozygous dark-winged moths, specifically designed to silence the mRNA transcript of the melanin-producing gene. Which of the following statements accurately describes the molecular mechanism and the ecological consequence of this intervention?
Options
- A.
The moths will develop light wings due to post-transcriptional gene silencing, rendering them highly susceptible to avian predation in a soot-covered environment despite possessing the dominant allele.
- B.
The intervention will induce a reverse mutation in the melanin gene, altering the genotypic frequency of the population and shifting the natural selection back to the pre-industrial state.
- C.
The moths will develop light wings because the introduced dsRNA binds directly to the promoter region of the melanin gene, inhibiting transcription and overriding environmental selection.
- D.
The moths will remain dark-winged because environmental selective pressures will trigger alternative splicing of the melanin transcript, bypassing the RNAi-induced translational block.
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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
Carbonaria gene|RNAi|Phenotypic plasticity
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The question tests the student's ability to integrate molecular genetics (RNAi mechanism from Biotechnology) with evolutionary biology (Industrial Melanism).
The primary trap is the 'Common Misconception' that RNAi alters the underlying genotype (like CRISPR) or acts at the transcriptional level.
Students must recognize that RNAi only masks the phenotype post-transcriptionally, and that natural selection acts on this expressed phenotype, regardless of the hidden dominant genotype.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Evolution - Class 12 |
| Concept | Industrial Melanism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |