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Question #45957
The Question
In a mutant angiosperm, the Megaspore Mother Cell (MMC) fails to undergo meiotic reductional division due to a defect in cell cycle regulation. Instead, it acts directly as a functional megaspore and undergoes the standard three rounds of sequential free-nuclear mitotic divisions. Assuming pollen grains from a normal wild-type plant of the same species participate in double fertilization with this mutant, which of the following statements is INCORRECT regarding the resulting structures?
Options
- A.
The mature embryo sac will be 8-nucleate and 7-celled, with every nucleus possessing a diploid (2n) chromosome complement.
- B.
The typical formation of a linear tetrad of megaspores and the subsequent degeneration of three micropylar megaspores will be absent.
- C.
Double fertilization by the wild-type male gametes will result in a diploid (2n) zygote and a tetraploid (4n) Primary Endosperm Nucleus (PEN).
- D.
If fertilization fails, the unfertilized egg cell can still develop into a diploid embryo, a phenomenon classified as apomixis.
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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
Meiotic Reductional Division|Megasporogenesis Symmetry|Generative Cell Division
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question tests the student's ability to track ploidy levels dynamically rather than relying on rote memorization.
Students often memorize 'zygote is 2n, PEN is 3n' as an absolute rule.
By removing the meiotic 'brakes' in the MMC, the entire embryo sac becomes diploid.
The student must mathematically derive the new ploidy of the zygote and PEN during double fertilization, synthesizing concepts of megasporogenesis, apomixis, and syngamy.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Plant Growth and Development - Class 11 |
| Concept | Differentiation vs Dedifferentiation |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |