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Question #45834
The Question
In a small, isolated population, an X-linked recessive allele (X^r) confers a trait with a severe metabolic cost, leading to pre-reproductive mortality in affected individuals. Compared to a lethal autosomal recessive allele, how will the transmission dynamics of X^r affect its allele frequency across generations, and which Hardy-Weinberg principle is directly violated?
Options
- A.
The X^r frequency will decline more rapidly because it is fully exposed to selection in hemizygous males, violating the assumption of no natural selection.
- B.
The X^r frequency will decline more slowly because it is exclusively transmitted by carrier females, violating the assumption of random mating.
- C.
The X^r allele will be eliminated in a single generation due to zero gametic contribution from affected males, violating the assumption of large population size.
- D.
The X^r frequency will remain at a stable equilibrium due to standard Mendelian segregation in females, violating the assumption of no gene flow.
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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
Hemophilia|Carrier frequency|Hominid Cranial Capacity (proxy for metabolic cost)
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume that all recessive alleles are equally 'hidden' from natural selection.
They fail to integrate the concept of male hemizygosity from 'Principles of Inheritance' with population genetics from 'Evolution'.
Hemizygosity exposes X-linked recessive alleles directly to selection, accelerating their decline and violating the Hardy-Weinberg assumption of equal reproductive fitness.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Sex-Linked Recessive Inheritance |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |