Answer to Question #83160 in Genetics for Angelica Flores
What is the probability that a daughter of this mating will be a hemophiliac?
If the couple has 3 sons what is the probability that all of them will NOT be hemophiliacs?
Let X* denote chromosome with allele for hemophilia and X denote the chromosome with normal allele.
The man's genotype is X*Y and his wife's genotype is X*X.
Their daughter could have either X*X or X*X* genotype. Thus, the probability for the daughter to be hemophiliac is 1/2.
The son could have genotype X*Y or XY. Thus, the probability to be hemophiliac is 1/2 as well.
Birth of each son is the independent event. Thus, the probability is 1/2 * 1/2 *1/2 =1/8.