Turner's syndrome mcq ?

Question

this disease occurs due to nondisjunction at the s*x chromosome resulting in an individual with one x and no y chromosome. color-blindness is a s*x linked recessive trait. a colorblind man marries a healthy woman. they have two children both with turner's syndrome. one of the children is color-blind. which of the following is true?

a.nondisjunction occurred in the father for both children.

b.nondisjunction occurred in the mother for both children.

c.nondisjunction occurred in the mother for the color blind child and in the father for the child with normal vision.

d.nondisjunction occurred in the father for the color blind child and in the mother for the child with normal vision.

Answer 1

C. Is the correct answer.

One of the children has an X chromosome carrying colorblindness, and there is only one place that could come from - the father.  This means that the father produced a normal gamete and the mother failed to contribute an X.

The other child has an X chromosome without colorblindness, which could only come from the the mother.  In this case, the mother had a normal gamete and the father's gamete had undergone nondisjunction.

Answer 2

all of the above