Our beautiful domestic cats come fabulously clothed in hundreds of color, pattern and coat varieties, a pretty amazing feat for a species that developed from a rather drab-looking desert animal. The African wildcat, the predecessor of our modern domestics, is a shorthaired sandy brown cat with Abyssinian-type ticking and tabby stripes. This color and pattern combination acts as effective camouflage in the cat’s native desert environment.
After cats began their association with humans, however, they were transported into other areas and climates, and Mother Nature did the rest – spontaneous genetic mutation brought us the myriad colors, patterns and coat varieties we enjoy today. Because of these mutations, our feline friends come in hundreds of color and pattern combinations. Humans also played a role in coloring outside the bloodlines through selective breeding.
While all of these choices are great for the cat lover who likes variety, they also can be confusing. What does a “lilac” cat look like? What’s the difference between a tortoiseshell and a calico? And just what the heck is a particolor? Read on for a short course in cat color and pattern.
A cat’s color depends upon the presence of pigmentation in the epidermis. For cats, only two pigments exist: black and red. All cats, no matter what color they are on the outside, are genetically either black or red, or in females, a combination of the two. All other colors result from other genetic factors or modifiers acting on these two pigments. Pigments are produced in cells called melanocytes, and the distribution and number of these cells are determined by the cat’s genetic makeup. These cells pass the pigment onto the cat’s hair, skin and eyes, and create the pattern and color.
Three specific genes are essential to the cat’s colorful exterior: pigment, color and density. The pigment gene determines the amount of pigment that’s distributed over the cat’s body. The color gene determines the intensity of the cat’s color. The density gene determines the density of the pigmentation; the more densely packed the pigment, the darker the color will be. For example, in order for a cat to appear black, the cat must possess three genes: B for black pigmentation, D for dense coloration, and C for full color. These are all dominant genes. However, these genes have corresponding recessive mutations that can change the cat’s appearance.
The gene for red (also called orange) is carried on the X chromosome, and that’s why it’s called a sex-linked color. Females have two X chromosomes, while males have one X and one Y chromosome. Since the X chromosome is longer than the Y, no location for the red gene exists on the Y chromosome. Therefore, male cats with their one X chromosome always express whatever color gene is present on that chromosome. If the gene is red, he will be a red tabby. If he receives the black gene he will be black or one of its variations, depending upon his genetic makeup. Females, on the other paw, can have both the gene for red and the gene for black, which gives us the colorful tortoiseshell with patches of both colors. Male cats can only be tortoiseshell if they are born with an extra X chromosome, a very rare occurrence. However, male tortoiseshells are not extremely valuable as is sometimes thought.
The Tabby Pattern
When talking about cats, “pattern” refers to the color distribution on a cat’s coat that forms a particular pattern, such as tabby stripes. Just as all cats are genetically black or red, all cats are genetically tabbies, no matter what pattern they appear to be on the outside. All possess one or more of four tabby genes: mackerel, classic, ticked and spotted. Although these patterns are quite different in appearance, they are all variations of the mackerel tabby from which the others arose.
The Seven Ancient Mutations
So now we know all cats are tabbies and are either black or red (or both if female). However, the presence of other genes can mask the stripes and cause changes in the cat’s coloration. Researchers have identified seven mutations that occurred many years ago, when felines had only recently become so-called domestic animals. These mutations are not the only ones that affect color and pattern, but they are essential for the myriad color, pattern, and coat varieties we see in cats today. They are:
A system of internationally recognized symbols was established to make it easier to understand the feline color genes and relationships to one another. Capital letters indicate dominant genes while lower case letters represent recessive genes.