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Question #45328
The Question
In a typical angiosperm, a mitotic failure during pollen development produces a diploid (2n) male gamete. This gamete successfully fuses with the secondary nucleus to form an endosperm containing 48 chromosomes. However, the seed eventually aborts due to 'endosperm-embryo mismatch syndrome'. How many linkage groups are present in this plant species, and what is the primary genetic basis for this developmental failure?
Options
- A.
12; Disruption of the standard 2:1 maternal-to-paternal gene dosage ratio in the endosperm.
- B.
16; Disruption of the standard 2:1 maternal-to-paternal gene dosage ratio in the endosperm.
- C.
12; Inability of the tetraploid primary endosperm nucleus to undergo free-nuclear divisions.
- D.
24; Polyspermy leading to a triploid zygote and subsequent embryo abortion.
Check Your Answer
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
Triple Fusion|Ploidy|Generative Cell Division
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students reflexively equate 'endosperm' with the '3n' ploidy state.
The trap requires them to override this reflex, apply the specific cytological condition (2n sperm + 2n central cell = 4n endosperm), and correctly calculate the haploid number (n) to find the linkage groups.
Furthermore, it tests the deeper NCERT-Plus concept that endosperm viability is governed by maternal-paternal gene dosage (imprinting), not merely the presence of nutrients.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Sexual Reproduction in Flowering Plants - Class 12 |
| Concept | Endosperm Development Sequencing |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |