Which of the following is the most common cause of primary amenorrhoea associated with a 47,XXY karyotype?
- A Non-disjunction during paternal meiosis I ✓
- B Non-disjunction during maternal meiosis
- C Post-fertilisation mitotic error
- D Robertsonian translocation
Correct answer: A. Non-disjunction during paternal meiosis I
Explanation
Klinefelter syndrome (47,XXY) most often results from maternal or paternal meiotic non-disjunction, but paternal meiosis I non-disjunction is the single largest contributor, and advanced paternal age is a recognised association. Robertsonian translocations cause structural rearrangements seen in trisomy 13 and 21, not sex chromosome aneuploidy, and a purely post-fertilisation mitotic error produces mosaicism such as 46,XY/47,XXY.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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