Why aren't there ginger cats? - briefly
Ginger coloration in cats is determined by the absence of a specific enzyme called tyrosinase, which is responsible for producing melanin. This enzyme is not present in ginger-colored animals due to a mutation in the gene that codes for it.
Why aren't there ginger cats? - in detail
The absence of ginger cats, compared to the prevalence of ginger tabbies among dogs and other mammals, is an intriguing topic in genetics. To understand this, we need to delve into the science behind coat color in felines.
The primary gene responsible for coat color in cats is the Agouti signaling protein (ASIP) gene. This gene determines whether a cat will have a solid or tabby pattern. The allele 'A' leads to a solid coat, while the allele 'a' results in a tabby pattern. In terms of color, the Orange (O) gene is crucial. The O gene produces an enzyme that converts black pigment into orange, leading to ginger or red fur.
However, the O gene is located on the X chromosome, and since males have only one X chromosome (XY), they can only inherit the ginger trait if their mother carries it. Females, with two X chromosomes (XX), can be homozygous or heterozygous for the O gene. A female cat that is heterozygous (Oo) will have a mix of orange and non-orange fur due to the phenomenon known as X-inactivation, where one of the two X chromosomes is randomly inactivated in each cell.
Despite the genetic potential for ginger fur, there are no known cases of ginger cats with tabby patterns. This absence can be attributed to the complex interplay between the ASIP and O genes. The ASIP gene dictates the pattern of the coat, while the O gene determines the color. In felines, the ASIP gene typically overrides the color influence of the O gene, leading to striped or spotted patterns regardless of the underlying fur color.
Moreover, the expression of the O gene is influenced by modifier genes that can either enhance or suppress its effect. In cats, these modifiers often work in tandem with the ASIP gene to create a wide range of coat colors and patterns, but they do not produce ginger tabbies.
In summary, while the genetic mechanisms for producing ginger fur exist in cats, the dominant influence of the ASIP gene on coat pattern prevents the expression of ginger tabby patterns. This genetic interplay results in the absence of ginger cats as we know them.