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Question #45495
The Question
A researcher isolates a mutant angiosperm exhibiting complete female sterility because its Megaspore Mother Cell (MMC) fails to differentiate and undergo meiosis. Interestingly, this exact same single-gene mutation also causes the plant's inner floral whorls (stamens and carpels) to develop into abnormal, leaf-like vegetative structures. Based on NCERT genetic principles, which of the following best explains this 'systemic fallout' from a single mutation?
Options
- A.
Epistasis; a dominant vegetative gene masks the expression of the specific reproductive genes responsible for megasporogenesis.
- B.
Pleiotropy; a single regulatory gene mutation disrupts a common underlying developmental pathway that controls multiple distinct phenotypes.
- C.
Polygenic inheritance; multiple genes cumulatively fail to maintain the floral meristem, indirectly halting MMC lineage.
- D.
Linkage; the gene for floral morphology and the gene for MMC meiosis are physically close on the same chromosome and mutated simultaneously.
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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
Megaspore Mother Cell|Pleiotropy Logic|Female Gametophyte
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often compartmentalize chapters, studying Megasporogenesis strictly under 'Reproduction' and Pleiotropy under 'Genetics'.
The trap tests the synthesis of these concepts.
The common misconception is confusing Pleiotropy (one gene dictating multiple traits via a shared regulatory cascade, like MADS-box genes) with Linkage (multiple genes mutating together) or Epistasis (one gene masking another).
Recognizing the phrase 'single-gene mutation' causing multiple phenotypic changes is the key to unlocking the pleiotropy concept.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Sexual Reproduction in Flowering Plants - Class 12 |
| Concept | Megasporogenesis Symmetry |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |