JX and SX have delivered their 1st son appearing normally developed. Test indicate child has hemophilia.?

What would you expect the genotype of the mothers parents to be?
a)father-X*Y, mother-XX
b)father-XY,mother-X*X
c)father-X*Y,mother-X*X*
d)father-X*Y,mother-XX*
e)father-XY,mother-XX
Where * denotes the defective allele; X*X would have a defective X allele on the first X chromosome.

If the child has type A or B hemophilia.... genotype B, unless there is a spontaneous gene mutation.

Hemophilia A: The most common type, is caused by lack of enough clotting factor VII.
Hemophilia B: The second most common type is caused by lack of enough clotting factor IX.
Hemophilia C: Caused by lack of clotting factor XI, and symptoms are generally mild with this type of hemophilia. This type is rarely seen in the United States.

Hemophilia A and B occur almost always in boys. Generally, hemophilia A and B pass from mother to son through one of the mother's genes. Everyone has two sex chromosomes, one from each parent. Females inherit an X chromosome from their mother and an X chromosome from their father. Males inherit an X chromosome from their mother and a Y chromosome from their father. The gene that causes hemophilia A and B is located on the X chromosome. This is why men can't pass along the gene that causes hemophilia to their sons. Most women who have the defective gene are simply carriers and exhibit no signs or symptoms of hemophilia. It's also possible for hemophilia A and B to occur through spontaneous gene mutation.

Hemophilia C can occur in both boys and girls. The defective gene that causes hemophilia C can also be passed on to children by mothers and fathers, but it follows an inheritance pattern different from that which occurs with hemophilia A and B.

b

C .

B is correct - since hemophilia is carried on the X chromosome, and is a recessive trait, but the Y does not give protection from the X chromosome.