 Such a combination of chromosomes could produce tortoiseshell or calico markings in the male, in the same way as XX chromosomes produce them in the female.All but about one in three thousand of the rare calico or tortoiseshell male cats are sterile because of the chromosome abnormality, and breeders reject any exceptions for stud purposes because they generally are of poor physical quality and fertility.Even in the rare cases where a male calico is healthy and fertile, most cat registries will not accept them as show animals.