Albinism is a recessive trait in humans. A geneticist studies family in which both parents are normal and at least one child has albinism. The geneticist reasons that both parents in these families must be heterozygous and the albinism should appear in ¼ of the children of these families. To his surprise, the geneticist finds the frequency of albinism trait is quite high. As a consultant, can you suggest an explanation for the higher expected frequency of albinism in these families