Couples who each have sickle cell trait
have three children;none of their children
have sickle cell disease.They tell you they
do not want to have another child because they know there is a one in four
possibility for their children to have sickle
cell disease, and they already have three
unaffected children.What is the probability their next child will have sickle cell disease? If they have another child and this
child has sickle cell disease, then what is
the probability that one of the other children will be an HLA match?