Question

A phenotypically normal couple has a colorblind klinefelter son (xxy). In which parent and at what meiotic stage must the non-disjunction event have occurred?
a. Meiosis i of mother
b. Meiosis i of father
c. Meiosis ii of father
d. Meiosis ii of mother
e. Meiosis i or ii of mother f. Meiosis i or ii of father

Answer 1

Answer;

D. Meiosis ii of mother

Explanation;

-The non-disjunction occurs in the meiosis II of the mother. This non-disjunction occurs when the two sister chromatids X and X fails to separate during meiosis II and produces an egg having two X chromosomes.

-Klinefelter syndrome is a condition that occurs in males when they have an extra X chromosome. The syndrome is not inherited, but usually occurs as a random event during the formation of reproductive cells (eggs and sperm) that results in the presence of one extra copy of the X chromosome in each cell (47,XXY).