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Question #46774
The Question
An actively dividing root apical meristem cell is treated with colchicine. Upon microscopic observation, the chromosomes are found to be fully condensed and scattered throughout the cytoplasm, but the cell completely fails to transition into anaphase. Which of the following best explains the direct molecular reason for this arrest?
Options
- A.
The Anaphase-Promoting Complex (APC) remains inactive because unattached kinetochores fail to generate the required mechanical tension.
- B.
The cell cycle arrests because the absence of spindle fibers triggers the G2/M checkpoint, reversing chromatin condensation.
- C.
Centromeres undergo spontaneous splitting, but the absence of polymerized microtubules prevents the migration of sister chromatids.
- D.
The failure of microtubule dynamic instability directly inhibits the activation of cyclin-dependent kinases (Cdks) required for prophase.
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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
Chromatin Condensation States|Microtubule Dynamic Instability|Centromere Positionality
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that colchicine 'stops chromosome movement' and mistakenly assume centromeres split normally but chromatids simply cannot migrate (Option C).
The critical NCERT-Plus insight is that microtubule attachment and the resulting mechanical tension are the mandatory biochemical triggers (via APC activation) for centromere splitting itself.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Cell – The Unit of Life - Class 11 |
| Concept | Chromatin Condensation States |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |