Question

A karyotype shows that a child has Klinefelter syndrome (47,XXY). If the child is also color-blind (due to a recessive X-linked allele), despite his parents having normal color vision, in which parent and stage of meiosis did nondisjunction occur?

Answer 1

Answer:

It occurred in the mother and in meiosis II stage

Explanation:

A karyotype shows that a child has Klinefelter syndrome (47,XXY) which involves a male child having an XXY chromosome in which the XX chromosome codes from the mother.

If the child is also color-blind (due to a recessive X-linked allele), despite his parents having normal color vision then the nondisjunction occurred in meiosis II because sister chromatids separate during meiosis II and the non separation is the reason for the Klinefelter syndrome.