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Question #46760
The Question
A male patient presents with chronic respiratory infections and sterility. Electron microscopy of his respiratory epithelium reveals an absence of dynein arms in the 9+2 axoneme of the cilia. However, a biopsy shows that his epithelial cells are undergoing normal mitosis. Which of the following statements best explains why cell division remains unaffected despite the mutation?
Options
- A.
Axonemal dynein mediates the sliding of microtubule doublets in cilia and flagella, whereas chromosome movement during mitosis relies on the polymerization dynamics of spindle microtubules.
- B.
Centrioles that form the mitotic spindle possess a 9+2 microtubular arrangement but utilize a completely different structural protein instead of tubulin.
- C.
The mutation selectively degrades the central sheath of the axoneme, which is required for ciliary bending but is naturally absent in the mitotic apparatus.
- D.
Ciliary motility requires ATP hydrolysis by nexin links, whereas chromosome segregation is driven by the contraction of actin microfilaments.
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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
Microtubule Dynamic Instability|Reptilian Heart Anatomy|Aves Pneumatic Bones
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often assume that because cilia, flagella, and mitotic spindles are all microtubule-based structures, a mutation affecting one will affect all.
The trap is failing to distinguish between the 'sliding filament' mechanism of stable 9+2 axonemes (requiring dynein ATPase) and the 'dynamic instability' (assembly/disassembly) mechanism of 9+0 centriole-derived spindle fibers.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Cell – The Unit of Life - Class 11 |
| Concept | Microtubule Dynamic Instability |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |