The male has a genetic condition called monosomy. Monosomy is usually due to primary nondisjunction during meiosis. In order for the sex-linked chocolate gene to express itself, the male must only carry one choc gene on one Z chromosome and he is missing his second Z chromosome. It is possible that the male has one complete Z chromosome and a part of the matching Z chromosome. The chromosome could be missing an arm or a part of the arm that holds the choc gene. The chances are good that he will be infertile.