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. Cats have AB blood groups just like people. Siamese coat color and crossed eyes may be caused by the same gene. The color of the points in Siamese cats is heat related.
Cool areas are darker.
Siamese kittens are born white because of the heat inside the mother's uterus before birth. This heat keeps the kittens' hair from darkening on the points. Though rare, cats can contract canine heartworms. People who are allergic to cats are actually allergic to cat saliva or to cat dander. If the resident cat is bathed regularly the allergic people tolerate it better.