Moo's Guides/Cat Genetics

... Also known as me (Moo) crushing your dreams about tortoiseshell toms and ginger she-cats making solid silver babies. Yeah. Sorry. :)

By the way, tortoiseshell toms are very very rare and so are ginger she-cats and solid silver cats aren't possible- okay, I'll explain.

COMING SOON: Smoke/Shaded/Chinchilla, Vitligo, and Cryptic/Hidden Tortoiseshells

Cat Coat Colour Genetics - Main Things
I might as well explain which things determine a cat's pelt: Some additional things: ... Yeah, that sounds very confusing, doesn't it? Well, maybe not any more after reading this! Let's get started!
 * Length
 * Pigment
 * Pigment Density
 * Dilution
 * Agouti
 * Agouti Type, Tabby Type, and Spots
 * White Spotting
 * Albinism
 * Pointing
 * White Masking
 * Amber
 * Curly Fur
 * Hairless
 * Polydactyly
 * Ear Deformities
 * Short Tails
 * Dilute Modifier
 * White Gloving

Length
By length I mean fur length, which is verrrryyyy easy. Short hair is dominant and represented by L, and long hair is recessive and represented by l.

Cats with short hair are either LL or Ll, and cats with long hair are ll.

By the way, long-haired cats can be any kind of long fur, whether it's slightly fluffy or a big fuzz-ball.

Pigment
Now for the slightly more complicated stuff. Firstly, sex heridity (don't worry, I'm not talking about THAT kind of... you know). Females have chromosomes XX and males have chromosomes XY. There is always a 50/50 chance of male or female offspring.

Pigment genes in cats are the red gene (O) and the not red gene (o). Now, those are on the X chromosome, therefore the X chromosome determines a cat's coat colour.

A male cat will only inherit an X from his mother, while a female will inherit one from both parents. Because a female gets two copies, she can get both XO and Xo, whereas a male can only get one or the other. This is why only females can be tortoiseshell, because they get both pigment genes and express them.

So if a black mumma cat and a ginger daddy cat have kittens, all the sons will be black because they only get Xo from the mother, but all the daughters will be tortoiseshell because they have the Xo gene from the mother and XO from the father.

Pigment Density
Okay, so there's the red gene and not red gene, but what about brown cats?

There is another gene that is not located on the X chromosome, and it controls what the not red gene will be, and only the not red gene.

It works a bit like fur length, except it has 3 alleles (half-genes) to choose from. These alleles are B (black), b (brown), and b1 (cinnamon). Cinnamon is like a rich solid brown with a warm reddish hue, it's a weird and pretty colour, but it isn't very common either.

B is the most dominant, followed by b, then b1. A cat can only get two of these, or else there might be a lot of serious complications.

Now, cats with black fur are BB, Bb (remember that when a dominant gene is paired with a recessive, the dominant always overpowers - it dominates! Haha, get it?), or Bb1. Cats with brown fur are bb or bb1, and cats with cinnamon fur are only b1b1.

Dilution
So now we have red, black and brown. But what about grey cats, hmm?

And now we can talk about dilution! Dilution is pretty self-explanatory - it dilutes the pigments! Dilution is a recessive trait, so it can skip generations.

A dominant coloured cat (black, ginger, etc) will be DD or Dd, and a dilute cat (grey, cream, etc) will be dd. When diluted, the four colours transform as follows: The ones found in purebreds will not be very... 'strong' or noticeable in feral cats.
 * Black > Grey
 * Chocolate > Lilac (which is kind of a dull grey-ish colour, and is unusual outside of purebreds)
 * Cinnamon > Fawn (a pale beige/tan, and is unusual outside of purebreds)
 * Red > Cream/Golden/Light Ginger

Agouti
Agouti basically means the cat's fur is ticked, meaning it has coloured bands (no, not swirls, just look up the Abyssinian cat if you don't know what ticked means). This is basically the cause of all tabby patterns.

Some colours, however, ONLY come in tabby, and these colours are: red, cream/golden, silver, and brown.

First thing's first, brown ONLY comes in tabby, and there are two types: chocolate and brown/dark brown. Chocolate tabbies have a brown base with darker brown stripes as well as the chocolate gene for dilution, and regular brown tabbies have a brown base with black stripes as well as the black gene for dilution. Both are just usually called brown because they are brown.

Silver also only shows up in tabby. Whaaaaaaat?! Yes, I'm sorry, but have you ever, ever in your life seen a solid silver cat with no tabby stripes whatsoever? If you say you've seen one on Google, well, hate to break it you dearie, but those are Photoshops for those Warriors roleplaying websites. Silver tabbies have silver bases with black stripes. Anyway, there are no solid silver cats unless you count black cats, and it goes back to tipping/inhibition. Turns out this is dominant, so either one or both of the parents will have to have it.

Reds/creams only come in tabby because the non-agouti gene doesn't affect red cats or their dilute versions. Through careful breeding however, they are "solid" reds and creams (though they really aren't).

This is fairly simple: agouti is dominant to non-agouti, so agouti is either AA or Aa, and non-agouti is only aa.

Non agouti cats appear solid, although technically no cat truly is, and even black cats have "phantom stripes" which show up when hit just right in the sunlight - it happens with my beautiful black and white cat! Also, agouti cats will appear to have an "M" on their forehead, and the only exception to this rule is toygers and some wild-domestic hybrids.

Agouti Type
Agouti can come in three different patterns: Abysinnian (rare outside of house cats), tabby (like most warrior cats), and spots (rare, and this does not include those weird leopard-like rosettes and wild-domestic hybrids, which I will not talk about).

This can be a little tough, so strap in. First, you need to figure out if your cat is ticked or not, and ticked means to have the Abysinnian pattern by the way.

Ticked is dominant to non ticked so ticked would be Tata and TaTa, and not ticked is only tata. But there is more! (If your cat isn't ticked)

Tabby
Now, you need to know if it is a mackerel tabby or classic tabby. Mackerel tabby is when there is one long stripe down the spine which stems off into other stripes, resembling the skeleton of the mackerel fish, and this tabby type is very tiger-y. Classic tabby is basically big blotchy swirls, and they are pretty uncommon in most of the world.

Mackerel is dominant to classic, so mackerel is therefore McMc or Mcmc, and classic is mcmc.

So now that's all figured out. But what about spots?

Spots
Spots happen when you modify the tabby pattern. It kinda breaks it up into little spots or dashes, the spots are bigger on classic tabbies and smaller on mackerel tabbies. These are often called "Broken Mackerel" or "Broken Classic", but it is mainly called spotted tabby so I'd stick to that. Also, spots are very uncommon and probably won't be seen in the cats even if it is dominant.

Oh yeah, spots are dominant. So spots would be SpSp or Spsp, while a mackerel/classic tabby would be spsp.

Aaaaand that wraps it up!

White Spotting
No, it does not mean your cat has white spots, white spotting is basically just how much white your cat has. The alleles kind of blend together in a way, so I'll just do a list lol. SS cats can also be pure white. Ss can be completely coloured (but the white will still be in their genes or in less noticeable chunks). Also, an important note: In order for a cat to have blue eyes, there must be a significant amount of white on the body, and there usually has to be some white on the face, but this isn't always the case of course.
 * A cat with no white on them is most likely an ss
 * A cat with low grade white spotting (white paws, white chin, white spots on belly or chest, white tail-tip, so mainly colour. Aka < 40% white) is most likely an Ss
 * Medium grade is the median between the others, so the whites can overlap quite a bit. It can be either Ss or SS
 * A cat with high grade white (very little colour, most likely on tail, back, head, face, a few stray spots, aka > 60% white) is most likely an SS

Cats with white spotting also have a chance for odd-eye heterochromia, though it is very rare.

And that wraps up the main parts of coat colour genetics!

Albinism
I advise against making albino characters, but I might as well explain it.

So, an albino animal lacks the ability to make pigments, and therefore appears white with red or blue eyes that have a lavender tint. A blue/lavender-tinted eyed albino will be caca or cacr, and a red eyed albino will be crcr.

A C (normal), cscs (Siamese point), cb (Burmese point) will remove albino always. But remember, the ca/cr alleles are pretty rare!

But albinism also greatly affects a Clan cat's survival, because it causes many skin and eye disorders which would make it difficult for it to be anything, not even a medicine cat, therefore they would have to join the elders den early.

Pointing
Pointing will be extremely uncommon unless a kittypet with the pattern has escaped/abandoned their Twoleg home to join the Clans then began to reproduce, but I'll explain anyway!

Kittens with pointing are born white, and as they grow their true colours begin to show. There are three versions of this: Siamese point (cs) is high colour contrast, Burmese point (cb) is low colour contrast. Here's a quick list: Point cats can also carry albinism, resulting in a higher contrast than usual, which becomes the Bondanese which is only csca.
 * Siamese (high colour contrast with a very pale/nearly white base and dark colour points) is only cscs
 * Tonkinese (kind of in the middle) is only cscb
 * Burmese (low colour contrast with little to no difference between the pointing and base) is only cbcb

'It would be tempting to make a beautiful Siamese go off and join ThunderClan, but I wouldn't really recommend it. They have thin coats so they are vulnerable to either freezing in leaf-bare or getting too many sunburns in green-leaf, and they are also prone to blindness, crossed eyes, and heart problems, which also happens with many, many pure-breds. So, I do not recommend making a pure-bred cat join any Clans at all.'

However, there are healthier breeds that can have this pattern so yay!

White Masking
White masking is when a coloured cat is masked with white, but its genetics are still there and they can still have coloured kittens.

White masking will be WW or Ww, and a regular coloured cat will be ww. This allele is uncommon, and these cats can have blue eyes and heterochromia as well, but...

'If you plan on making a white cat with blue eyes, beware! White fur + blue eyes = very high chance of deafness! Even odd-eyed whites because the ear on the side of the blue eye can be deaf! I cannot stress this enough!'

Amber
Amber does not occur outside of Norwegian Forests so it is incredibly rare to have, but just in case!

This colour is weirdly lovely, and its symbol is E. It affects the amount of black pigments shown in the fur, reducing it to these stripe bands on the hairs, giving the cat a reddish base with dark cinnamon stripes. It's sorta hard to explain.

If a cat has normal colouring, it is an EE or Ee. An amber cat will be ee. Also, the only known colours it affects is black and grey so it goes as follows: black > amber, grey > light amber.

But please please please, this colour is very rare, so I highly not recommend you have a character with amber. Also, amber cats are born black/grey and their colours change over time!

Curly Fur
There are many variations of curly fur, some are recessive, and some are dominant. There are also a few types of it so I'll put a list: So yeah!
 * Cornish Rex fur is r
 * Devon Rex is re
 * Dutch Rex is Rd
 * LaPerm (curly fur) is Lp
 * Oregon Rex is ro
 * Selkirk Rex is Se
 * Wirehair is Wh

Hairless
In addition to curly fur is hairlessness! That's a tongue twister.

So there are many types, therefore we get a list:
 * Hairless (French) is h
 * Hairless (Hawaiian) is hr
 * Hairless (Redcar) is hd
 * Hairless (Sphynx) is hr

Polydactyly
Polydactyly is when a cat has extra toes on a paw or paws, the front paws usually have 5 each and the back paws usually have 4 each. Polydactyly is a dominant trait, and usually does not harm the cat at all.

A cat with polydactyly is PP or Pp, and a normal cat is pp.

This is actually very common, but there aren't many fanfictions where there's a polydactyl cat, and I wish there were more, because it's very common! In a collab I'm writing, I'll make a cat with polydactyly, because it's more common than what people think it is.

Ear Deformities
These are cute :) So basically "ear deformities" are folded or curled ears. Those are both dominant traits, therefore a cat with folded or curly ears can be FuFu/CuCu or Fufu/Cucu, and a normal cat will be fufu/cucu. But...

TWO CATS WITH FOLDED EARS BREEDING = DEAD KITTENS AND CARTILAGE DEFECTS.

Also, these cats won't do bad with Clan life, as far as I'm aware!

Short Tails
This is a funny thing. It's always a good idea to research these types of things if you plan on making a character with a short/stubby tail or no tail at all.

Firstly, there's the Japanese Bobtail, which is recessive, so: jbjb is a short, curled tail and JbJb or Jbjb is a normal tail.

There is also Kurilian Bobtail, which is dominant. It isn't very common, and their tails are very bunny-like. It goes as follows: kurkur is a normal tail, Kurkur is a short tail which may or may not be curled, and KurKur is a short, curled tail.

Now, the Manx/tailless gene. This gene is dominant, is the most common, and has a lot of variations. It is also found in the Cymric. This is thought to be linked to skeletal problems, which gave it a bad reputation for killing Manx kits with two copies of the gene. This is called "Manx syndrome" and fortunately it's getting rarer and rarer! Cymrics kinda get a double dose of this, and often their kittens die days after birth from being unable to defecate (... which is a fancy term for pooping). Cats with no tails actually live normal, happy lives and don't have balance issues!
 * Tailless is MM and it kills Manxes in the uterus but it is getting rarer and rarer as I stated earlier
 * Ranging from no tail to a short tail is Mm
 * A normal tail is mm

Dilute Modifier
Dilute modifier is modifying the colours of dilute cats! It makes their coat... browner? Lol sorry. This is often described as bicuit coloured or caramelised.

It's simple, and is dominant + represented by Dm. A cat with dilute modifier will be DmDm or Dmdm, and a cat without it is dmdm. However, a DmDm or Dmdm cat will not show it unless they are dilute. Here's a list: Apparently this hasn't really been seen out of Oriental breeds, and in some places it isn't even considered a colour.
 * Blue/Grey > Caramel
 * Lilac > Taupe
 * Fawn > There is a theoretical fawn-based caramel, though it hasn't been seen yet.
 * Cream > Apricot

Now, for our last one (for now)...

White Gloving
There are a few genes that will give a cat some white, although they are much less common than white spotting and epistatic white and also more breed-restrictive. This is actually quite interesting to me.

White gloving is a recessive gene. Unlike other white genes, this one can be carried! So, a cat without the gloving gene is NN or NG (I don't know why there are capitals when it is a recessive gene, ask science), and a cat WITH the gloving gene is GG.

It isn't common, but it does appear in a lot of pure-breds! It was discovered in Birmans then somehow made its way to Ragdolls, Egyptian Maus, Exotic Shorthairs, Maine Coons, Manxs, Seychellois (that took five minutes to spell btw), Siamese, Siberians, Sphynxes and Turkish Vans (literally going off Messybeast here).

But this is actually what caused Snowshoes to be a thing! Two Siameses with gloving reproduced and then cute white feets came about! They were crossed with other shorthairs, giving them the white masks and cobbier bodies - sound familiar? Yes, it is believed that Grumpy Cat might have been a Snowshoe (or Ragdoll, but she looks more like a Snowshoe).

This trait is pretty hard to deduce. It can easily be caused by low grade white spotting that didn't show up in the generation before. In Snowshoes, both gloving and white spotting can be present.

Cat Eye Colour Genetics... Sort Of
I'm not an expert on eye colours, unfortunately. But feral cats DO have an eye colour spectrum: The colours are more duller and not as vibrant on warrior cats than they are on pure-bred cats. Cat eyes, like human eyes, have unpredictable heredity unless you are willing to go through all the refraction and intensity work. Any eye colour can go with any pelt as long as it isn't blue or blue-green: those are the only ones where pelt colour really matter. Also, green and hazel are the most common eye colours, hazel being more common than green on tabbies.
 * Green
 * Hazel
 * Golden Yellow
 * Lemon Yellow
 * Amber
 * Orange
 * Copper

Now, for SPECIALISED EYE COLOURS:
 * Siamese Blue (from sky-blue to sapphire, these are for Siameses ONLY)
 * Turquoise (Tonkinese ONLY!)
 * Blue-green (Variant of green, for SOME tipped coats ONLY)
 * Blue (non-albino white only)
 * Albino Blue (very pale lavender tinted mauve-blue, almost appears grey)
 * Albino Pink
 * Odd-eyed Heterochromia (often one blue eye and another from the regular eye range, which is most common in non-albino whites and SOME cats with white spotting)

Keep This In Mind!
Honestly this is just me being nitpicky, so long as your two ginger cats don't have a pitch black kit with blue eyes.
 * There are more cats with short hair than long hair
 * The colours of a tom comes from their mother, while the colours of a she-cat come from both parents
 * Cats are more likely to be black than chocolate or cinnamon
 * You are more likely to have black cats than grey cats
 * Most cats are tabby
 * Abysinnian is rare outside of cat shows, stripes are most common, spots are kinda rare-ish too, and the leopard-like rosettes and clouded marbled spots are hella hecka rare
 * Red, cream/golden, brown, and silver only come in tabby outside of cat shows
 * Mackerel tabby is more common than classic tabby
 * It's common for cats to have a little white on them
 * Avoid albino cats, please
 * Cats with darker tips are unusual, but they might have kittypet ancestry somewhere. Just remember they are born white, and it could be a shock when the kit changes colour! xD
 * There is a dominant white gene, but it is uncommon
 * Amber cats are extremely pretty, but also extremely rare
 * Cats with curly fur look funny and cute and are a bit of an oddity
 * A lot of cats have extra toes
 * Curled and folded ears won't be abnormal if those breeds have already mixed in with warriors
 * They also don't have any problems with hearing whatsoever, as far as I'm aware
 * Tailless cats are uncommon and some breeds are very unhealthy. Depending on the setting however, they may be more common
 * Dilute modifier is probably for kittypets
 * Same for white gloving ^^^

Conclusion
Thanks for reading! I hope you enjoyed the guide! C: