Possibly one of the most delightful characteristics of cat ownership is the stunning array of cat coat colors and patterns.
From the soulful, inky black of the Bombay, to the rosy cinnamon of the Oriental Shorthair, to the snow white of the Turkish Angora, cat lovers sometimes ponder: why do certain colors or patterns only appear in specific breeds?
The answer lies in the complex world of cat genetics, selective breeding and the history of cat domestication.
The Genetics Behind Cat Coat Colors
Genes are fundamental elements of a cat’s appearance: chains of DNA that define everything from the length of fur, its color, its pattern, and even its texture. Any domestic cat can have many colors, but actually seeing these colors will be determined by how the genes [that contribute to color/pattern/texture] from the cat’s parents are expressed.
The following genes are the ones that greatest contribute to coat color:
B/b/b1 (Black/Brown/Cinnamon):
This gene determines the production of eumelanin, the pigment that creates black cats and brown colors. The dominant (B) wall creates black; b and b1 are recessive variants that create chocolate and cinnamon colors, respectively.
O/o (Orange/Non-orange):
This gene is on the X chromosome, which indicates the color of an orange (red) pigment. A dominant O allele creates an orange color cats, while o creates a non-orange color (black or brown). Since female cats have two Xs, they can be tortoiseshell cats if they inherit O and o. Male cats have one X chromosome, so their color can only be orange or not.
D/d (Dense/Dilute):
This gene affects the color intensity. The dominant ”D” allele will lead to maximum intensity colors. The recessive ”d” allele will dilute colors, e.g., a black will become gray (or blue), a chocolate will become lilac, and an orange will become cream.
C/c/c1 (Tyrosinase/Albinism):
This gene produces some variations that either contribute to an albino individual, or that produce color points-tied similarly to the temperature sensitivity that occurs in some breeds, such as Siamese.
KIT (White/White Spotting):
This gene helps form and position the pigment cells. Some variants produce a solid white coat, white spotting, or the very steeply-defined “gloves” found in Birmans.
How Breed-Specific Colors Emerge
These genes are found among all cats but sometimes specific colors or patterns become breed specific through selective breeding and breeding for these traits for several generations.
Breeders selectively pair cats so as to develop a breed with very specific characteristics- sometimes, but not limited to rare or uncommon colors that the breed itself (largely) expresses.
1. Selective Breeding and Genetic Isolation
When a breed is established, a small group of cats with specific traits—such as color, pattern, or body type—is chosen as the foundation.
After many generations of selectively breeding only the kittens that most closely resemble the breed standard, breeders will often find that they are the only ones out there breeding those kittens.
This means that the genetic isolation has presented the opportunity for rare color genes to become multiplied and retained in the breed while also being able to discount others from the overall population, as retaining only desirable genes is controlled through breeding.
Havana Brown: This breed was developed to create a single solid chocolate colored coat. Chocolate color cats are rare in the general cat population because the chocolate color requires two copies of the recessive b allele. The intention was when they bred with kittens that carried this trait, it would remain consistent.
Bombay: Created to resemble a miniature panther, Bombays are bred exclusively for a solid black coat, which is produced by the dominant B allele and reinforced through selective breeding.
Russian Blue: A breed noted for its solid blue (gray) coat, resulting from dilution gene (dd) acting upon the black pigment.
Maine Coon: The diversity in color and pattern in this breed primarily arose through existence and selective breeding (gened out). Maine Coons can be any color such as: black, blue (black diluted), red, cream (red diluted), tortoiseshell, etc.
2. Connected Traits and Breed Standards
Breed standards (formal descriptions of the ideal cat for each breed) often specify not only colour, but eye colour, coat texture, and coat pattern like tuxedo or tabby mix. In fact, there are often connections between certain colours and other breed-defining traits.
For example:
Siamese: The classic “pointed” colouration (darker extremities and lighter body colour) is associated with a temperature-sensitive type of albinism (a variant of the C gene), and is a defining trait of Siamese.
Birman: The “white gloving” trait associated with the paws is linked to a recessive allele (wg) which is rare outside the breed, but fixed within (almost exclusive to Birmans).
3. Genetic Bottlenecks and Founder Effects
As a breed starts with only a few cats the amount of genetic diversity is limited. If those cats have rare color genes, those genes can become common in that breed but remain rare in general. This is called the founder effect. Also, over time, rare traits in the general cat population could end up being specific to a breed based only on the limited gene pool.
Why Don’t All Cats Have All Colors?
Despite domestic cats having an unlimited genetic palette, not every color or pattern is expressed in every breed or in the general cat population.
Why? Several reasons:
Recessive Genes: Some colors are present only when two copies of a recessive gene are present (chocolate, cinnamon etc). If the founders of the breed did not have those recessive genes, those colors will not be present in the breed unless new gene pool material is added.
Breed Standards: Cat associations will often define an allowable pantheon of colors for show cats. For example, a breed standard may define that only blue and silver coats are acceptable, and other reasons do not matter when registering the cats.
Genetic Compatibility: Some colors or patterns are linked to health issues or are difficult to achieve genetically. For example, male tortoiseshell cats are rare and often sterile because the tortoiseshell pattern requires two X chromosomes, which males typically lack.
Conclusion
To conclude, breed-specific cat colors are a result of an incredible interaction of genetics, selective breeding, and breed standards.
While most colors are readily available in the cat population, it is a combination of a breeder’s focus and the genetics of inheritance that allows certain colors or patterns to be unique to a breed.
As we become more aware of the science behind these beautiful coats, we appreciate the variation of our cats and their journey from wildcat to pet.