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Question #46279
The Question
A wild-type Solanum species exhibits the typical floral formula ⊕ ⚥ K_{(5)} C_{(5)} A_{5} G_{\underline{(2)}} and produces morphologically perfect flowers. However, the plant is completely sterile and fails to set viable seeds. Cytological examination of its anthers reveals that while bivalents form normally, there is a high frequency of nondisjunction during meiosis. Which of the following cytological anomalies best explains this functional reproductive failure despite morphological perfection?
Options
- A.
Premature splitting of centromeres during Anaphase I, leading to the formation of polyploid microspores.
- B.
Defective spindle fiber attachment at the kinetochores of bivalents during Metaphase I, leading to unequal segregation and aneuploid gametes.
- C.
Failure of the synaptonemal complex to dissolve during Diakinesis, preventing crossing over and causing meiotic arrest.
- D.
Failure of cytokinesis after Telophase II, directly resulting in the formation of aneuploid pollen grains.
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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
Solanaceae Floral Formula|Spindle Attachment Geometry|Synaptonemal Complex Assembly
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question tests the synthesis of three NCERT chapters: Morphology (floral formula), Cell Cycle (meiotic stages and spindle mechanics), and Genetics (Aneuploidy vs.
Polyploidy).
The primary trap is confusing the outcomes of spindle failure (which causes aneuploidy via nondisjunction) with cytokinesis failure (which causes polyploidy).
It also tests precise knowledge of meiotic events, such as the exact stage of centromere splitting and synaptonemal complex dissolution.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Morphology of Flowering Plants - Class 11 |
| Concept | Solanaceae Floral Formula |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |