Butterflies have an X-Y sex determina- tion system that is different from that of flies or humans. Female butterflies may be either XY or XO, while but- terflies with two or more X chromosomes are males. This photograph shows a tiger swal- lowtail gynandro- morph, which is half male (left side) and half female (right side). Given that the first division of the zygote divides the embryo into the future right and left halves of the butterfly, propose a hypothesis that explains how nondisjunction during the first mitosis might have produced this unusual-looking butterfly.