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Question #45828
The Question
A quantitative trait in a population, governed by polygenic inheritance, exhibits a classic bell-shaped curve. Over successive generations, stabilizing selection consistently culls the extreme phenotypes. Which of the following genetic principles best explains the underlying 'biological friction' that reduces the fitness of these extreme variants?
Options
- A.
The individual polygenes exhibit antagonistic pleiotropy, where alleles driving the extreme phenotype simultaneously cause detrimental physiological trade-offs.
- B.
The trait is controlled by multiple alleles at a single locus, which inherently restricts the survival of homozygous recessive extremes.
- C.
Epistatic gene interactions completely mask the additive effects of dominant alleles at the extreme ends of the distribution curve.
- D.
The extreme phenotypes lack phenotypic plasticity, making them highly susceptible to environmentally induced genetic drift.
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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
Polygenic Inheritance Curve|Pleiotropy Logic|Homeostatic Balance
Why This Question Is Tricky
Common Mistakes
The 'Conceptual Pivot' is the synthesis of Polygenic Inheritance and Pleiotropy.
Students typically memorize these as opposite concepts (many genes -> one trait vs. one gene -> many traits).
The trap is failing to recognize that individual genes within a polygenic complex can have pleiotropic side-effects.
When these side-effects are harmful, they act as an evolutionary constraint, driving Stabilizing Selection.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Polygenic Inheritance Curve |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |