Klinefelter’s syndrome, in which a male has an extra X chromosome (XXY), is the result of nondisjunction. The failure in spermatogenesis that could produce this would occur in:

 

B. Anaphase II.

A. Anaphase I.

C. Prophase I.

D. Prophase II.

 

Answer: (B)

 

I tried drawing out the picture and I see that Anaphase II is a possibility but why would Anaphase I be incorrect? Is there a distinction b/w males and females in where it would be Anaphase I or II? Would Klinefelter’s syndrome more affect males than females in general?

 

Thanks.

If a nondisjunction in spermatogenesis is to cause Klinefelter's, the male must pass down an X and a Y chromosome in the same sperm. These combine with the X chromosome in the egg to create XXY in the fertilized egg.

 

In a male, nondisjunction in anaphase II couldn't cause Klinefelter's, because the X and the Y chromosomes were already separated during anaphase I. Nondisjunction in anaphase II could produce sperm with two Xs or two Ys, but that won't create Klinefelter's.

I thinkCap'n Refsmmat hit the nail on the head. For a fact sheet that is giving out to families to understand Klinefelter's syndrome check out http://www.genetics.edu.au/information/Fact%20Sheets/KlinefelterSyndromeXXYSyndromeFS31

 

 

Klinefelter's syndrome, in which a male has an extra X chromosome (XXY), is the result of nondisjunction. The failure in spermatogenesis that could produce this would occur in:

 

B. Anaphase II.

A. Anaphase I.

C. Prophase I.

D. Prophase II.

 

Answer: (B)

 

I tried drawing out the picture and I see that Anaphase II is a possibility but why would Anaphase I be incorrect? Is there a distinction b/w males and females in where it would be Anaphase I or II? Would Klinefelter's syndrome more affect males than females in general?

 

Thanks.