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NBME 18 Answers

nbme18/Block 1/Question#14 (reveal difficulty score)
26 yo man with 27 yo wife, inability to conceive
Primary spermatocyte ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–

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 +15  upvote downvote
submitted by โˆ—merpaperple(45)
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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.

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b1ackcoffee  Brilliant question and explanation! +2
jbrito718  PICTURE PLEASE +1

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submitted by โˆ—
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Meiosis 1โ‡’ from primary to secondary spermatocyte ; Meiosis 2 โ†’ Secondary to spermatid

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 +4  upvote downvote
submitted by โˆ—hayayah(1212)
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Most problems with cell division occur in anaphase of Meiosis I.

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realfakedreams  @hayayah - made an account just to say thank you. I appreciate that you exist. +24
tekkenman101  Yup, Down syndrome? NDJ in Meiosis 1 in moms. Just memorize and move on. +
medicalmoraxella518  it's not down syndrome, Klinefelter Syndrome +

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