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Question #46159
The Question
During a marine biology study, a mutant strain of Asterias (starfish) is observed to reach reproductive maturity while exhibiting a strictly bilateral body plan. Based on the principles of developmental genetics and the characteristic features of Phylum Echinodermata, which of the following genetic anomalies best explains this phenotype?
Options
- A.
A mutation in a non-coding regulatory sequence that prevents the downregulation of larval-specific genes, resulting in a paedomorphic bilateral adult.
- B.
A nonsense mutation in the structural genes responsible for maintaining the primary radial symmetry of the free-swimming larva.
- C.
A frameshift mutation in the coding strand that prematurely activates the pentaradial body plan during early embryogenesis.
- D.
A deletion of the genes coding for the water vascular system, which directly converts the adult's secondary bilateral symmetry into radial symmetry.
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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
Echinodermata Larval Symmetry|Non-Coding Strand Utility|Mendelian Dihybrid Exceptions
Why This Question Is Tricky
Common Mistakes
The 'Conceptual Pivot' relies on the classic NCERT distinction between larval and adult symmetry in Echinoderms.
The trap leverages 'Common Half-Truths' by swapping the symmetry types between developmental stages (e.g., claiming larvae have primary radial symmetry or adults have secondary bilateral symmetry).
It synthesizes basic animal diversity with advanced developmental genetics (heterochrony and non-coding regulatory utility).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Animal Kingdom - Class 11 |
| Concept | Echinodermata Larval Symmetry |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |