Question

A husband and wife have normal vision, although both of the couple's fathers are red–green color-blind, an inherited X-linked recessive condition.
a. What is the probability that the couple's first child will be a normal son? Enter your answer as a fraction
b. What is the probability that the couple's first child will be a normal daughter? Enter your answer as a fraction
c. What is the probability that the couple's first child will be a color-blind son? Enter your answer as a fraction
d. What is the probability that the couple's first child will be a color-blind daughter? Enter your answer as a fraction

Answer 1

Answer:

a: 1/4

b: 1/2

c: 1/4

d: 0

Explanation:

Since the wife had a color-blind father (X^cY), she should be a carrier for the disease. Her genotype would be "X^cX". Fathers do not transmit the X-linked disorders to their sons, so the genotype of the husband is "XY".

a. The probability that the couple's first child will be a normal son: 1/4

b. The probability that the couple's first child will be a normal daughter: 1/2

c. The probability that the couple's first child will be a color-blind son: 1/4

d. The probability that the couple's first child will be a color-blind daughter: Zero