Question

Red-green color blindness is a human X-linked recessive disorder. A young man with a 47,XXY karyotype (klinefelter syndrome) is color blind. His 46,XY brother also is color blind. Both parents have normal color vision. Where did the nondisjunction occur that gave rise to the young man with Klinefelter syndrome?

Answer 1

Answer:

The non-dis-junction occur with Klinefelter syndrome  is occurred at "Meiosis II;Mother"

Explanation:

Thus, the more likely than not acquired the Y chromosome from his dad who has typical shading vision, there is no chance for a nondisjunction occasion to have occurred from the fatherly heredity. His mom must be heterozygous $X^{+} X^{c}$ in light of the fact that she has typical shading vision. This implies she more likely than not acquired a visually challenged X chromosome from her partially blind dad.  

For him to acquire two partially blind X chromosomes from his mom, the egg more likely than not been the result of a non-dis-junction in meiosis II.  

In meiosis I, the homologous X chromosomes independent, so one cell has the $X^{+}$ and different has $X^{c}$. Disappointment of sister chromatids to isolate inmeiosis II would then bring about an egg with two duplicates of $X^{c}$Xc.

Answer 2

Answer:

Mother, meiosis II

Explanation:

Red-green color blindness is a human X-linked recessive disorder. A young man with a 47,XXY karyotype (klinefelter syndrome) is color blind. His 46,XY brother also is color blind. Both parents have normal color vision.The nondisjunction occured in mother during meiosis II that gave rise to the young man with Klinefelter syndrome.

Etiology:

Meiotic Non-disjunction of the chromosome pairs during the First or second division of gametogenesis. Because of the extra chromosome, individuals with the condition are usually referred to as 47XXY. As in the above mentioned scenario, meiotic nondisjunction during meiosis II in the mother resulting in the failure of the sister chromatids to separate during meiosis II thus resulting in too many chromosomes.