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Question #45852
The Question
During a clinical study of human reproductive anomalies, two distinct karyotypes are observed: Embryo X shows a 69, XXY karyotype and undergoes early spontaneous abortion, whereas Individual Y presents a 47, XXY karyotype and survives to adulthood. Which of the following statements correctly explains the cellular mechanisms and survival outcomes of these two cases?
Options
- A.
Embryo X resulted from the failure of the zona pellucida to induce a block to polyspermy, whereas Individual Y resulted from meiotic non-disjunction and survives due to X-chromosome inactivation.
- B.
Embryo X resulted from meiotic non-disjunction during Anaphase I of oogenesis, whereas Individual Y resulted from the failure of the cortical granules to release their contents.
- C.
Both anomalies arise from the failure of the block to polyspermy, but Individual Y survives because the extra chromosomes are selectively eliminated during early mitotic cleavage.
- D.
Embryo X resulted from the failure of cytokinesis during the first mitotic cleavage, whereas Individual Y resulted from a point mutation in the sex-determining region of the Y chromosome.
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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
Down/Klinefelter/Turner Syndrome Karyotypes|Polyspermy Prevention Mechanisms|Acrosomal Enzyme Activation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Distinguishing between Polyploidy (whole set addition via fertilization errors like polyspermy) and Aneuploidy (individual chromosome addition via meiotic non-disjunction).
Students often confuse the origins of numerical chromosomal aberrations, assuming all arise from meiotic failures, thereby ignoring the critical role of the zona pellucida in preventing lethal polyploidy.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Principles of Inheritance and Variation - Class 12 |
| Concept | Down/Klinefelter/Turner Syndrome Karyotypes |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |