Hemophilia A is an X-linked recessive blood clotting disorder. A normal man and a woman with hemophilia A have a child with Turner Syndrome (XO). This child does not have hemophilia. In whom did non-disjunction occur? In meiosis I or meiosis II?

1. In whom did non-disjunction occur?

Non-disjunction occur in the Woman;

2. In meiosis I or meiosis II?

there is not enough information to tell if the nondisjunction happened in meiosis I or II.

Explanation:

Both Turner syndrome and hemophilia, a blood-clotting disorder, are X-linked

Turner syndrome is due to a chromosomal abnormality in which all or part of one of the X chromosomes is missing or altered. While most people have 46 chromosomes, people with TS usually have 45. The chromosomal abnormality may be present in just some cells in which case it is known as TS with mosaicism. In these cases, the symptoms are usually fewer and possibly none occur at all.

Hemophilia A is an X-linked, recessive disorder caused by deficiency of functional plasma clotting factor VIII (FVIII), which may be inherited or arise from spontaneous mutation.

Hence, the disjunction occur in the woman.