Genes are tiny cellular information packages that all humans and animals are born with that determine every single trait they will have.
Although whatever color and pattern a cat’s coat will be may seem random, there are actually very strict rules that cover which cat gets which coat.
Genes are units of heredity, and there are strict rules that are in place that determine which gene for coat color/pattern will be expressed (where “expressed” means “physically visible”).
Every cat has more than one gene controlling coat look, but exactly which gene will express is determined by the type of genes the cat possesses.
Simply speaking, genes comes in pairs, and each gene can be either dominant or recessive, where dominant means that the trait associated with the gene will be expressed and where recessive means that, when the gene appears in conjunction with a dominant gene, it will not be expressed.
Should the pairing for coat color/pattern be dominant/dominant or dominant/recessive, the dominant trait will express, but should the pairing be recessive/recessive, the recessive trait will express.
This is genetics at its simplest, however, and many other factors can affect gene pairings and the expression of traits.
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Another factor that’s extremely important when determining the colors and patterns of a cat’s coat is whether or not the cat has a masking dominant gene.
There are several kinds of masking dominant genes including orange (O), white (W) and white spotted (S), and, if a cat does indeed have this gene, it will express no matter what other genes may be present.
If, for instance, a cat carries the white spotted gene, the cat will have spots on its body where its natural coat color and pattern has been “whited-out”.
These spots can be so large that they cover the cats whole body, however, and, in these cases, the only way to tell whether the cat has a white spotted masking gene or a white masking gene is by eye color.
Albinism is another genetic condition that causes a cat to have a white coat, but this condition is an anomaly and also expresses in other aspects like eye color.
Along with the white, orange and white spotted masking genes, there are several more genes that directly affect coat patterns and colors.
The Agouti gene (A) controls the color-banding or “ticking” on a cat’s fur, the Dense gene (D) controls whether the cat’s coat will be a dark or a diluted color, and the B gene controls whether or not a cat’s coat will be black.
There is also the (T) gene, which determines what kind of tabby pattern the cat’s coat will have, and, depending on whether the gene appears as recessive or dominant, a cat will have one of three possible tabby patterns.
There are a host of other genes that control aspects like colorpoint, snowshoes, spots and rosettes, and this is why cats seem to come in an infinite variety of beautiful coats.