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?
(type an integer or a decimal. do not round)

Explanation:

Step1: Analyze chromosome - inheritance for sons

Sons inherit a Y - chromosome from their father and an X - chromosome from their mother. The father has the genotype xY (defective x chromosome) and the mother has the genotype XX (normal X chromosomes).

Step2: Determine the possible genotypes of sons

Since sons get a Y - chromosome from the father and an X - chromosome from the mother, the possible genotypes of sons are XY. The father will pass on his Y - chromosome to his son (because only fathers can pass on Y - chromosomes to sons), and the mother will pass on one of her normal X chromosomes. So, a son cannot inherit the defective x chromosome from this father - mother combination.

Answer:

0