The Punnet square for this cross is shown below. Remember that blood types A and B exhibit a type of codominance to type O. This means that type O blood will not be expessed when their genotype has either type A, type B, or both. If, in case, both are expressed, the individual would have type AB.
Mother and father with blood types A and B, respectively, have a child with blood type O (blood group inheritance is codominant). What fraction of their children is expected to have blood type A?