Far From Home | A Clan Creation Guide

A Rough Genetics Guide

The fur colour of cats can be explained by Mendelian genetics. Since eye colour cannot, I will focus only on the fur colour and follow up with a short note on realistic eye colours, but no genetic explanations for them.

I'll try to avoid using genotypes and explain instead through simple words why cat genetics work the way they do. Another thing I'd like to mention is that I will only be including blacks, browns, reds, tortoiseshells and their dilutions. You won't find genetics for chocolates, lilacs, etc. here because they are not very common in the wild and, therefore, in Warriors.

Before we get into some more detailed things, here are a couple of ground rules:
- the brown tabby colouring is the wild type for cats; in other words, a cat is a brown tabby and mutations of their genes cause them to become something else
- all she-cats have two X chromosomes (XX) and all toms have one X chromosome and one Y (XY)
- blue is the genetics term for grey and can range from a Russian blue colouring to a light grey

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Tabby vs. self
As stated above, all cats are brown tabbies unless something happens to mutate a gene. In this case, something would mutate the agouti gene, which is responsible for tabby markings.

Tabbies are very common, but self cats (cats without the agouti gene and, therefore, without tabby markings) are possible because of a recessive gene. The tabby becomes a self of the same colour, just without stripes. For example, a blue tabby would become a blue self. The exception is the brown tabby, which becomes a black self.

Because tabbies carry both the agouti and the recessive gene, they can have both tabby and self kits. Self cats, however, do not carry the agouti gene, and can only have self kits.

Another important thing to note is that even if the agouti gene is absent in a cat, you may still be able to see some striping. Ginger cats always have stripes, though they can range from dark in colour to very light (almost invisible).

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Dilution
Another common gene, this one is responsible for lighter fur colours. Like with the agouti gene, the dilution gene is a recessive one.

A list of common dilutions:
- brown tabby/black dilutes to blue tabby/blue
- red tabby dilutes to cream tabby
- tortoiseshell (ginger tabby, black) becomes a diluted tortoiseshell (cream tabby, blue)

Because the dilution gene is recessive, two dilute cats will only have dilute kits, but a combination of a dense and dilute parents or two dense parents will have both dense and dilute kits.

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Ginger and tortoiseshell
A mutation on the X chromosome causes it to show red pigmentation, making a naturally brown cat ginger. Because the mutated gene is a co-dominant gene, all of the cat's X chromosomes must be mutated in order for the cat to appear completely red (ginger tabby).

Having copies of both a natural gene and a mutated gene will result in a mixture - a tortoiseshell, to be exact. Since toms have only one X chromosome under normal circumstances, they cannot be tortoiseshells (that is caused by another mutation, where the tom has XXY chromosomes).

Litter combinations are a little harder to explain here, but generally the toms will take on a colour present in their mother's coat, as that is where they get their X chromosome from, and she-cats will become a mixture of their parents, as they get an X chromosome from both.

This means that a brown tabby she-cat mated with a ginger tabby tom can have a litter of brown tabby toms and tortoiseshell she-cats. If the she-cat is a tortoiseshell, however, and the tom a ginger tabby, toms can be either brown tabby or ginger tabby and she-cats can be tortoiseshell or ginger tabby.

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White spotting
White spotting is a result of another co-dominant gene. A cat with the recessive form will have no white markings, while the dominant gene can cause the cat to be anywhere from 50% to fully white.

As a general rule, the smallest amounts of spotting are visible on the chest, feet and face. From there, the white patterns become larger in those areas and can also appear on the belly or tail tip. For cats with over 50% spotting, the white markings will also show on their sides and, sometimes, back.

Some spotting is more common in feral cats than lots of white.

It's best to think of spotting as a spectrum in relation to creating litters. At one end, you have a pair with no white spotting, which means their kits also won't have white. At the other, you have two cats with lots of spotting, which means their kits will also have lots of white. As you change up the pairs - no white + some white, no white + lots of white, some white + some white, some white + lots of white - you move along the spectrum, with the chance of having a litter of kits with no white, some white or lots of white possible with two cats that have some white (the middle of the spectrum).

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Quick note on eye colours:
While the genetics behind eye colours and how they are inherited are a lot more difficult to understand and, therefore, explain, here are some general rules for eye colours:

- the normal range of colour is from green to copper, with yellow being the most common
- eye colours are on a spectrum, which means they can range from light green to dark green to hazel to a dark amber to an almost golden colour
- blue eyes are only possible on white cats and bring with them an 80% chance of deafness
- odd eyes (two different colours) are also only possible on white cats or cats with white spotting
- odd eyes are always blue plus a colour from the spectrum; cats cannot have one amber eye and one green
- pink eyes are seen only in albino cats, which have a very low chance of survival in the wild
- blue eyes on non-white cats do exist, but are very unlikely to occur naturally in feral cats
- purple and colour changing eyes are never possible on cats, wild or domestic

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Next section will have a list of genetically possible litters, depending on parent colour.