The gene in cats that causes the orange coat color is sexed linked, and is on the X sex chromosome. This gene may display orange or black. Thus, as female cat with two X chromosomes may have orange and black colors in its coat. A male, with only one X chromosome, can have only orange or black, not both. If a male cat is both orange and black it is ( besides being extremely rare ) sterile. To have both the orange and the black coat colors, the male cat must have all or part of both female X chromosomes. This unusual sex chromosome combination will render the male cat sterile.