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NBME 18 Answers

nbme18/Block 1/Question#14 (22.7 difficulty score)
26 yo man with 27 yo wife, inability to conceive
Primary spermatocyte🔍

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submitted by hayayah(983),
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Mots olbsmepr tihw llce ionivsdi ccrou ni naaapesh of eiMioss .I

realfakedreams  @hayayah - made an account just to say thank you. I appreciate that you exist. +12  

In meiosis I, the gametocyte splits from a single cell (XXYY) -> 2 cells (XX + YY). In meiosis II these two cells split again (-> X + X, Y + Y). Hence in order for a father to pass on both an X and a Y chromosome to his son (eg in Klinefelter syndrome, w/ XXY chromosome), a spermatid must contain both an X and a Y chromosome, which means that there was an error in meisosi I. The stage at which meiosis I occurs is the primary spermatocyte.

Meiosis 1⇒ from primary to secondary spermatocyte ; Meiosis 2Secondary to spermatid