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Question #45299
The Question
An actively dividing onion root tip is treated with colchicine. Upon microscopic examination, the mitotic index is found to be artificially elevated, and numerous cells exhibit polyploidy. Which of the following best explains the precise cellular mechanism responsible for this observation?
Options
- A.
Colchicine depolymerizes actin microfilaments, preventing the contraction of the cleavage furrow during cytokinesis.
- B.
Colchicine binds to tubulin dimers, inhibiting phragmoplast formation and preventing Golgi-derived vesicles from fusing at the equatorial plate.
- C.
Colchicine inhibits the synthesis of cellulose and hemicellulose within the dictyosomes, directly arresting the cell cycle in telophase.
- D.
Colchicine promotes the premature degradation of the centromere, leading to non-disjunction and subsequent polyploidy without affecting cytokinesis.
Check Your Answer
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
Cell Plate|Golgi Vesicles|Mitotic Index Implications
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'colchicine causes polyploidy' but fail to connect it to the structural disruption of the phragmoplast.
The trap relies on distinguishing plant cytokinesis (microtubule-dependent phragmoplast and Golgi vesicles) from animal cytokinesis (actin-dependent cleavage furrow), and recognizing that colchicine targets the transport scaffold (tubulin), not the synthesis of the cell wall materials themselves.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Cell Cycle and Cell Division - Class 11 |
| Concept | Plant Cell Cytokinesis |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |