Nondisjunction spermatogensis

[SaintJude]

I'm posting this question, b/c I had to take a lot of time to think about it and I wanted to make sure I properly understood its lesson.

During meiosis II of spermatogenesis, nondisjunction of chromosome 4 occurs. The resultant gametes could contain:

I. two identical copies of chromosome 4
II. two non-identical copies of chromosome 4 with maternal & paternal genetic material.
II. two non-identical copies of chromosome 4 with only paternal genetic material.
And then they give you variations as usual.
-Qbank



Anyway, it's, highlight it's in white: I & II only.

2 questions:
1. Are I & II both referring to "n+1" situations?
2. Is II referring to "n+1" situation where a (non-even) no. of crossovers has led to the formation of two non-identical sister chromatids?

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[SaintJude]

bump, babe babe.

 

[ppfizenm]

You should be able to find the answer pretty easy to this by looking at a diagram of meiosis but I am pretty sure the answer is 1 and 2 as it would be impossible to have nondisjunction result in two non-identical copies of a chromosome with DNA from only one parent.

 

[SaintJude]

1. Are I & II both referring to "n+1" situations?
2. Is II referring to "n+1" situation where a (non-even) no. of crossovers has led to the formation of two non-identical sister chromatids?