In certain species of summer squash, fruit color is determined by two interacting genes. A dominant allele, W, determines white color, and a recessive allele (w) allows the fruit to be colored. In a homozygous ww individual, a second gene determines fruit color: G (green) is dominant tog (yellow). A white squash and a yellow squash were crossed, and the F, generation yielded approximately 50% white fruit and 50% green fruit. What are the genotypes of the parents?