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Question #45795
The Question
A female patient experiences recurrent early miscarriages. Karyotypic analysis of the aborted conceptus reveals a 69, XXY chromosomal constitution. Immunological profiling detects autoantibodies targeting the glycoproteins of the ovum's acellular envelope. Which of the following mechanisms best explains the formation of this non-viable zygote?
Options
- A.
A. The autoantibodies inhibit the intracellular Ca2+ surge, preventing the extrusion of the second polar body and resulting in aneuploidy.
- B.
B. The autoantibodies bind to Zona Pellucida proteins, interfering with the structural reorganization triggered by cortical granule exocytosis, leading to polyspermy.
- C.
C. The autoantibodies prematurely trigger the release of cortical granules, causing rapid hardening of the membrane and subsequent endomitosis.
- D.
D. The autoantibodies block the ZP3 receptors completely, preventing the acrosome reaction but allowing multiple sperms to bypass the corona radiata.
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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
Cortical_Granules|Zona_Pellucida|Calcium_Wave
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between the mechanisms of infertility vs. polyspermy, and differentiating Polyploidy (3n) from Aneuploidy (2n+1).
Students often memorize that ZP3 antibodies cause contraception/infertility by blocking sperm binding.
However, if the antibodies specifically interfere with the post-fertilization ZP hardening (cortical reaction), the result is polyspermy.
Furthermore, polyspermy leads to polyploidy (entire extra sets of chromosomes), not aneuploidy (individual extra/missing chromosomes).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Locomotion and Movement - Class 11 |
| Concept | Calcium Dynamics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |