Question

Individuals with Klinefelter syndrome have an XXY set of sex chromosomes. Which of these describes a way this abnormality can arise? Select all that apply.

Nondisjunction during Meiosis I in the father results in an XY sperm, which fertilizes an X egg

Nondisjunction during Meiosis II in the mother results in an XX egg, which is fertilized by a Y sperm from the father

Nondisjunction during Meiosis I in the mother results in an XX egg, which is fertilized by a Y sperm from the father

Nondisjunction during Meiosis II in the father results in an XY sperm, which fertilizes an X egg

Answer 1

Right options are:

*Nondisjunction during Meiosis II in the mother results in an XX egg, which is fertilized by a Y sperm from the father

*Nondisjunction during Meiosis II in the father results in an XY sperm, which fertilizes an X egg

Because if non disjunction occur in meiosis, then homologus chromosomes will not separate and leads to diploid gamete which is not possible. But when non disjunction occur in meiosis 2, then there are no separation of sister chromatids occurs during anaphase 2 and produces abnormal gamete as given above and when fuse with normal gamete of other parent will form child with klinefelter syndrome.