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Question #45887
The Question
A bacterial population is exposed to a novel, nutrient-poor environment. A mutation occurs in the promoter region of a specific metabolic gene, slightly shifting the boundary of the transcriptional unit and significantly increasing the binding affinity of RNA polymerase. Which of the following best describes the molecular and evolutionary consequence of this event?
Options
- A.
It alters the reading frame of the structural gene, producing a highly efficient novel enzyme that drives disruptive selection.
- B.
It increases the rate of mRNA synthesis without changing the enzyme's primary structure, leading to directional selection for the mutated allele.
- C.
It shifts the terminator boundary downstream, resulting in a longer polycistronic mRNA that ensures stabilizing selection.
- D.
It changes the template strand into the coding strand, increasing Darwinian fitness and establishing Hardy-Weinberg equilibrium.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Promoter_Mutation|Darwinian_Fitness|Transcriptional_Efficiency
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between regulatory mutations (which alter the amount of gene product) and structural mutations (which alter the structure of the gene product).
A common misconception is that any beneficial mutation must change the protein's amino acid sequence.
This question also tests the student's ability to bridge Molecular Basis of Inheritance (transcriptional unit boundaries) with Evolution (mapping molecular efficiency to Darwinian fitness and directional selection).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Transcriptional Unit Boundaries |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |