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Question #45815
The Question
A researcher applies colchicine to the microspore mother cells (MMCs) of a diploid angiosperm (2n = 20) during meiosis. The chemical is subsequently washed away, and the surviving pollen grains are used to pollinate the stigma of an untreated plant of the same species. Assuming successful double fertilization, which of the following statements is INCORRECT regarding the cytological mechanisms and outcomes?
Options
- A.
Colchicine inhibits tubulin polymerization during Anaphase, preventing homologous chromosome separation and yielding diploid (2n=20) male gametes.
- B.
The resulting zygote will be triploid (3n=30), violating the standard Mendelian assumption of equal genetic contribution from both parents.
- C.
The primary endosperm nucleus (PEN) formed will be pentaploid (5n=50) due to the fusion of a diploid male gamete with a triploid central cell.
- D.
The F1 generation plants will likely exhibit high sterility due to the inability of homologous chromosomes to form stable bivalents during their own gametogenesis.
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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
Chromosomal Theory of Inheritance|Microsporogenesis Ploidy Shift|Megasporogenesis Symmetry
Why This Question Is Tricky
Common Mistakes
The Conceptual Pivot lies in recalculating ploidy levels during double fertilization after a targeted meiotic failure.
Students often blindly memorize PEN as 3n or miscalculate the central cell's contribution.
Furthermore, they must understand that colchicine specifically targets tubulin, halting the physical basis of the Chromosomal Theory of Inheritance (meiotic segregation), leading to restitution nuclei and unreduced gametes.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Chromosomal Theory of Inheritance |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |