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Question #45493
The Question
In a typical angiosperm exhibiting Polygonum-type development, a Megaspore Mother Cell (MMC) is heterozygous for two tightly linked genes (A and B) in a cis arrangement. During megasporogenesis and subsequent megagametogenesis, which of the following statements is INCORRECT regarding the genetic diversity and linkage groups of the resulting structures?
Options
- A.
The egg cell and the synergids will always possess identical alleles for genes A and B, regardless of whether crossing over occurred during meiosis.
- B.
The degeneration of three out of four megaspores significantly reduces the probability that a recombinant chromatid will be represented in the functional female gametophyte.
- C.
If crossing over occurs between genes A and B during pachytene, the resulting mature embryo sac will contain a mix of parental and recombinant genotypes among its seven cells.
- D.
The number of linkage groups in the functional megaspore is equal to the haploid chromosome number (n) of the plant.
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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
Megaspore Mother Cell|Linkage Group Calculation|Crossing Over
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often conflate the genetic diversity generated within the meiotic tetrad with the final genetic makeup of the mature embryo sac.
The trap relies on forgetting that monosporic development acts as a severe genetic bottleneck.
While crossing over creates a mix of parental and recombinant chromatids in the four megaspores, the survival of only ONE megaspore followed by strictly mitotic divisions ensures that the entire 7-celled embryo sac is genetically uniform.
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 |