Question

men have xy (or yx) chromosomes and women have xx chromosomes. x - linked recessive genetic diseases (such as juvenile retinoschisis) occur when there is a defective x chromosome that occurs without a paired x chromosome that is not defective. represent a defective x chromosome with lowercase x, so a child with the xy or yx pair of chromosomes will have the disease and a child with xx or xy or yx or xx or xx will not have the disease. each parent contributes one of the chromosomes to the child. complete parts a through d below.
a. if a father has the defective x chromosome and the mother has good xx chromosomes, what is the probability that a son will inherit the disease?
0
(type an integer or a decimal. do not round.)
b. if a father has the defective x chromosome and the mother has good xx chromosomes, what is the probability that a daughter will inherit the disease?
(type an integer or a decimal. do not round.)

Explanation:

Step1: Analyze son's chromosome - inheritance

A son gets a Y - chromosome from his father and an X - chromosome from his mother. The father has xY and the mother has XX. Since a son must get the Y - chromosome from the father and an X from the mother, the son's chromosome pair will be XY.

Step2: Determine probability of disease

A son with XY does not have the disease. So the probability that a son will inherit the disease is 0.

Step3: Analyze daughter's chromosome - inheritance

A daughter gets an X - chromosome from the father and an X - chromosome from the mother. The father has xY (so he can pass on x) and the mother has XX. The possible chromosome pairs for a daughter are xX or XX.

Step4: Determine probability of disease for daughter

A daughter with xX or XX does not have the disease. So the probability that a daughter will inherit the disease is 0.

Answer:

a. 0
b. 0