The complexities of feline genetics give us a wide array of cat fur colors and patterns. So how is an individual cat’s appearance determined? Why are calico and tortoiseshell cats almost always female? And why are orange cats more likely to be male? We will explore these and other topics in this series of articles explaining the genetics that determine a cat’s fur color and pattern.
In this first article, we start with an exploration of the eight basic color options. In domestic cats, one gene determines the cat’s base color, and several genes can modify this color.
The first gene controls the amount of a black-colored pigment, and comes in three different varieties or alleles. The first creates black fur, the second produces a brown color known as chocolate or chestnut, and the third creates a lighter reddish-brown color called cinnamon.
A second gene controls the density of the pigment. One allele provides for the dense version of each color, resulting in the black, chocolate, and cinnamon colors we just learned about. The other allele, however, creates a lighter or more diluted version of each color. Black fur becomes blue, a color we would typically describe as gray. Chocolate fur becomes lilac, and cinnamon becomes fawn.
The options increase further when we account for a third gene which controls a red-colored pigment and is responsible for orange fur. Formally known as red fur, the orange fur commonly seen on orange tabbies and as part of calico and tortoiseshell coats represents a masking or conversion of the black-pigment base color. A male cat with the gene for black fur, which also has the gene for orange fur, will be orange rather than black. (As we will learn in a subsequent article, the situation is more complicated for females, who can have both black and orange fur.)
Thus far we have explored seven of the eight basic fur colors. The final color, cream, is produced when a cat has both the orange gene and the gene for diluted color. Later in this series we will explore in detail the the actions and interactions of these first three genes. We will also learn about aspects of a cat’s appearance – such as the presence of white fur, tabby patterns, and points – that result from the involvement of additional genes.
To summarize, these are the eight basic feline coat colors:
- Blue (dilute of black)
- Lilac (dilute of chocolate)
- Fawn (dilute of cinnamaon)
- Red/Orange (converts all black-based colors to red/orange)
- Cream (dilute of red/orange)
Resources: Cats of a Different Color, Cat Colors FAQ, CFA: Understanding the Basic Genetics of Cat Colors