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Question #45276
The Question
Colchicine is applied to the anthers of a diploid angiosperm (2n = 24) during microsporogenesis, specifically inhibiting spindle fiber formation at Anaphase I. These pollen grains are subsequently used to pollinate a normal, untreated female plant of the same species. Which of the following correctly identifies the chromosome number of the resulting zygote and primary endosperm nucleus (PEN), and the underlying genetic phenomenon?
Options
- A.
Zygote: 36, PEN: 48; Autopolyploidy due to non-disjunction of all homologous chromosomes.
- B.
Zygote: 24, PEN: 36; Aneuploidy due to the failure of sister chromatid separation.
- C.
Zygote: 48, PEN: 72; Allopolyploidy due to complete genome duplication in both gametes.
- D.
Zygote: 36, PEN: 60; Autopolyploidy due to the fertilization of an unreduced egg.
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
Meiosis I|Pachytene Crossing Over|Autopolyploidy
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize that 'Colchicine causes polyploidy' but fail to mechanically trace the ploidy through the double fertilization process when only ONE parent is treated.
The trap lies in calculating the PEN ploidy (n + n + 2n = 4n) and distinguishing between systemic spindle failure (Polyploidy) versus individual chromosome non-disjunction (Aneuploidy).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Cell Cycle and Cell Division - Class 11 |
| Concept | Meiotic Reductional Division |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |