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Question #45859
The Question
In a large, randomly mating population, genomic analysis over several millennia reveals a consistent, directional increase in the A-T base pair content within highly repetitive, non-coding DNA sequences. The phenotypic traits of the population remain entirely unchanged. Which of the following is the most accurate evolutionary interpretation of this molecular data?
Options
- A.
The population remains in Hardy-Weinberg equilibrium because mutations in non-coding DNA do not undergo natural selection or alter the phenotype.
- B.
The directional mutational pressure violates Hardy-Weinberg equilibrium at these loci, even though the double-stranded DNA still obeys Chargaff’s rule.
- C.
The phenomenon indicates a violation of Chargaff’s rule, as the ratio of total purines to total pyrimidines will progressively deviate from 1:1.
- D.
This directional shift is a classic example of genetic drift, which exclusively alters allele frequencies in non-coding regions to drive speciation.
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
Hardy-Weinberg_Equilibrium_Variables|Chargaff’s_Rule_Limitation|Evolutionary_Pressure
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the AT/GC ratio with Chargaff's rule (A/T = G/C = 1).
A common misconception is that changing the AT/GC content violates Chargaff's rule.
Furthermore, students frequently assume Hardy-Weinberg equilibrium only applies to coding genes with visible phenotypic expression, forgetting that molecular evolution (like mutational bias in non-coding DNA) fundamentally violates the 'no mutation' assumption of the Hardy-Weinberg principle.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Molecular Basis of Inheritance - Class 12 |
| Concept | Chargaff’s Rule Limitation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |