Galactosemia is a recessive human disease that is treatable by restricting lactose and glucose in the diet. Susan Smithers and her husband are both heterozygous for the galactosemia gene.
a. Susan is pregnant with twins. if she has fraternal (nondentical) twins, what is the probability both of the twins will be girls who have galactosemia?
b. if the twins are identical, what is the probability that both will be girls and have galactosennia?