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Question #45480
The Question
In a mutant angiosperm, cytological analysis reveals that the ploidy shift during microsporogenesis occurs normally, successfully producing haploid cells. However, these cells remain physically tethered as a tetrad, ultimately leading to male sterility. Molecular analysis identifies a point mutation in a specific gene that, overcoming the protective degeneracy of the genetic code, results in a missense mutation at the active site of a critical enzyme. Which of the following is the most direct consequence of this mutation?
Options
- A.
Failure of the tapetum to secrete functional callase, preventing the degradation of the callose wall surrounding the microspore tetrad.
- B.
Inability of the microspores to synthesize sporopollenin for the exine, leading to physical tethering via the intine.
- C.
Arrest of the microspore mother cell in Prophase I, preventing the physical separation of homologous chromosomes.
- D.
Defective synthesis of the enzyme cellulase by the endothecium, preventing the dissociation of the pollen grains during dehiscence.
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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
Tapetum_Secretions|RNA_Spliceosome_Mechanics
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students must distinguish between the genetic separation of chromosomes (meiosis/ploidy shift) and the physical separation of the resulting cells (callose dissolution).
The primary trap is Functional Overlap: confusing the roles of the anther wall layers (Tapetum vs.
Endothecium) and their respective biochemical secretions (Callase for tetrad dissociation vs. alpha-cellulosic fibers for dehiscence).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Sexual Reproduction in Flowering Plants - Class 12 |
| Concept | Microsporogenesis Ploidy Shift |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |