Q: I adopted a calico cat from a shelter that named him Joseph for his coat of many colors. My veterinarian was surprised when she examined him and confirmed he was a male, because she said calico cats are almost always female. Why is that? A: Calico cats have orange, black, and white fur, while tortoiseshell cats, or torties, sport orange and black fur. Because of the genes that code for coat color, both types of cats are almost always female. Domestic cats have approximately 20,000 genes on 38 chromosomes, two of which are the sex chromosomes X and Y. Females have two X chromosomes and are referred to as XX. Males have one X and one Y chromosome and are called XY. Approximately 20 genes determine coat color in cats. The two basic colors are black and orange, sometimes called red. White is the absence of both colors. Other …