Question

In humans, XO individuals are females with Turner syndrome and XXY individuals are males with Klinefelter syndrome. Red green color blindness is caused by an X-linked recessive allele. Suppose a colorblind man and a normal woman with no family history of color blindness married and had a daughter who was colorblind and had Turner syndrome.
1. Which event could have given rise to this offspring?
A) Nondisjunction at meiosis II in the mother.
B) Nondisjunction at meiosis I in the father.
C) Nondisjunction at meiosis l in the mother.
D) Nondisjunction at meiosis II in the father.
E) Nondisjunction at either meiosis I or meiosis II in the mother.

Answer 1

Answer:

The correct answer is option E) "Nondisjunction at either meiosis I or meiosis II in the mother".

Explanation:

Nondisjunction is a phenomena at which chromosomes are not properly separated during anaphase. This can either happen at meiosis I or meiosis II during oogenesis. Nondisjunction would explain the XO chromosomic condition of the daughter with Turner syndrome as well as the X-linked recessive allele of the red green color blindness. Nondisjunction happened in the mother because the father could not inherited an X-linked condition.