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Question #45421
The Question
The incidence of Trisomy 21 (Down syndrome) increases significantly with advanced maternal age. This phenomenon is primarily attributed to the structural degradation of cohesin complexes and meiotic spindles during a prolonged phase of oogenesis. Identify the exact stage at which the primary oocyte remains arrested for decades, and the subsequent meiotic error that directly results in this aneuploidy upon resumption of division.
Options
- A.
Arrest in Diplotene of Prophase I; Non-disjunction of homologous chromosomes during Anaphase I
- B.
Arrest in Metaphase II; Non-disjunction of sister chromatids during Anaphase II
- C.
Arrest in Pachytene of Prophase I; Premature separation of sister chromatids during Anaphase I
- D.
Arrest in Diakinesis of Prophase I; Non-disjunction of homologous chromosomes during Anaphase II
Check Your Answer
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
Meiotic_Arrest_Points|Aneuploidy|Oogenesis
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently confuse the two distinct meiotic arrests in human oogenesis (Prophase I vs.
Metaphase II).
Furthermore, they must synthesize concepts from three different NCERT chapters (Cell Cycle, Human Reproduction, and Genetics) to link the specific sub-stage of the first arrest (Diplotene) with the mechanical cause of the maternal age effect (Anaphase I non-disjunction of homologous chromosomes).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Chemical Coordination and Integration - Class 11 |
| Concept | Feedback Mechanism Loops |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |