A (Better) Guide to Cat Genetics May 26, 2018 22:45:18 GMT
Post by KingHarry on May 26, 2018 22:45:18 GMT
Written by bird
In this guide, we’ll be exploring how cat genetics really work, and how to make realistic cat OCs. This guide will teach the entirety of what you need to know to make realistic cat OCs, at least genetically. It will also teach you how to make families of cat OCs much more realistic.
For anyone who does not want to bother with the complexity of genetics, there is a kitten generator located in the last chapter, along with some other resources.
Chapter 1: An Introduction to Genetics
Vocabulary for this chapter:
- Punnett square
First of all, we’ll be learning about Mendelian genetics. If you know what Mendelian genetics are, feel absolutely free to skip this section. This is only for those who are completely new to genetics.
What we’ll focus on first are “dominant” and “recessive” traits. Dominant and recessive traits describe how likely a “phenotype”, or an observable characteristic of an individual, is to pass down from a parent to their offspring.
Humans and animals have two copies of each gene, except in sex-linked traits, which will be explained in the red factor chapter of this guide.
Different types of the same gene are called “alleles”. Dominant alleles override recessive alleles. When there are two copies of the same allele, it is called homozygous, and when there are two different alleles, it is called heterozygous.
Individuals with heterozygous “genotypes”, or sets of genes, are called “carriers” of the recessive alleles.
Let’s look at a diagram about this, called a punnett square.
The capital letter allele is dominant to the lowercase letter allele. When there is a dominant allele, the individual will have the phenotype of the dominant allele. If there are two of a recessive allele, the individual will have the recessive phenotype.
If this is not a good enough explanation, look up “simple Mendelian genetics”.
Here is a link to a punnett square generator, so that you can test out different pairings of alleles. scienceprimer.com/punnett-square-calculator
Chapter 2: The Black Factor and Red
Vocabulary for this chapter:
- Tortoiseshell / Tortie
Let’s start with black! There are three types of the black factor in cats. These are black, chocolate, and cinnamon. Black is dominant over chocolate, and chocolate is dominant over cinnamon.
Let’s use B to represent black, b to represent chocolate, and b1 to represent cinnamon.
Here are some examples of some pairings of these genes.
(BB) - Obviously, this is a black cat. Will only pass on black.
(Bb) - Another black cat, which is a carrier of chocolate. Will pass on black or chocolate.
(Bb1) - A black cat that carries cinnamon. Will pass on black or cinnamon.
(bb) - A chocolate cat. Will only pass on chocolate.
(bb1) - A chocolate cat that carries cinnamon. Will pass on chocolate or cinnamon.
(b1b1) - A cinnamon cat. Will only pass on cinnamon.
For an example, let’s look at a black homozygous cat and a chocolate homozygous cat’s punnett square.
All of the kits of these two parents would be heterozygous black cats carrying chocolate.
Now, let’s look at red.
Red is codominant to black, so a list of what is dominant to what would look like this:
Red / Black
Red and black are sex-linked traits, which means there is one red or black gene for each X chromosome. Males have XY chromosomes, and females have XX chromosomes, except for some intersex variations that we’ll touch on later.
This means that females can have red and black, red and red, or black and black. Males can only have red OR black. Chocolate and cinnamon are mutations of black, so they fall under black in this example.
Let’s let Xb represent the black gene, and let Xr represent the red gene. When animals are born, each parent gives one chromosome to each offspring, so they would be passing down Xb, Xr, or Y.
This is why most females are not red, because they would have to have both X chromosomes having red genes, meaning they would have to have a red father AND a red or tortoiseshell mother.
All males inherit the color of their mother, because the father passes down a Y chromosome and the mother passes down a X chromosome. In cases of the mother being a tortoiseshell, males have a 50% chance of being black and a 50% chance of being red.
But what happens if a female is XbXr or XrXb? That produces a tortoiseshell, which is a cat with red and black fur. They are also known as torties. This is why males cannot be tortoiseshells in most scenarios. Tortoiseshells can have any variation of black, so there can be chocolate or cinnamon tortoiseshells.
So, let’s think about some hypothetical pairings of cats right now. What if a black male and a red female had kittens?
Males would be all red (XrY).
Females would all be black tortoiseshell (BB XrXb).
Now, what if a chocolate male and a tortoiseshell female who was black carrying chocolate had kittens?
Males would be 50% red (XrY), 25% chocolate (bb XbY), and 25% black carrying chocolate (Bb XbY).
Females would be 25% chocolate homozygous (bb XbXb) , 25% chocolate homozygous tortoiseshell (bb XrXb), 25% black heterozygous carrying chocolate (Bb XbXb), and 25% black heterozygous carrying chocolate tortoiseshell (Bb XrXb).
Let’s get more complicated. What if a chocolate male carrying cinnamon and a tortoiseshell female who was chocolate carrying cinnamon had kittens?
Males would be 50% red (XrY), 25% chocolate heterozygous carrying cinnamon (bb1 XbY), 12.5% chocolate homozygous (bb XbY), and 12.5% cinnamon homozygous (b1b1 XbY).
Females would be 25% chocolate heterozygous carrying cinnamon (bb1 XbXb), 25% chocolate heterozygous carrying cinnamon tortoiseshell (bb1 XrXb), 12.5% chocolate homozygous (bb XbXb), 12.5% chocolate homozygous tortoiseshell (bb XrXb), 12.5% cinnamon (b1b1 XbXb), 12.5% cinnamon tortoiseshell (b1b1 XrXb).
I know this seems complicated, but it’s really not! It’s easy once you get down to it and use punnett squares to visually represent things. Usually, you will not be dealing with equations as complex as the one above.
For the punnett square generator I recommended, it’s not possible to input Xr and Xb, so I’ve been using O for red and o for black.
Chapter 3: Dilutions
Vocabulary for this chapter:
- Dilution modifier
Now, to add even more complexity to this (scary, I know), let’s talk about diluted coat colors!
Diluted coat colors can be represented by D and d. D is non-diluted, and is dominant. d is diluted, and is recessive. All coat colors, including the mutations of black, can be diluted.
Red’s diluted version is officially called cream.
Black’s diluted version is officially called blue.
Chocolate’s diluted version is officially called lilac.
Cinnamon’s diluted version is officially called fawn.
They follow the same pattern of dominance as the main coat colors.
If both parents are diluted, all kittens will be diluted, as both parents will have the dd genotype and there is no dominant D to cause non-diluted kittens. Likewise, if both cats are homozygous non-diluted, there can be no diluted kittens. However, if both cats are Dd, or one cat is dd and one cat is Dd, there will be some variance in whether or not the kittens will be diluted.
There is also something called a “dilution modifier”, which is a dominant gene that can “caramelize” a cat. This only applies to cats that are already diluted, and makes no difference in a cat that is not. It is very uncommon, but it’s important to know about. “Caramelize” is not a scientific term, and in genetics books it will always be referred to as the dilution modifier.
Cream’s caramelized version is officially called apricot.
Blue’s caramelized version is officially called caramel.
Lilac’s caramelized version is officially called taupe.
There is no official name for the version of fawn that is caramelized, seeing as it makes very little difference in the physical appearance of the cat. It does, however, exist.
Let’s let the dilution modifier be Dm, and the lack of a dilution modifier be dm. This means that all cats who are caramelized are either DmDm or Dmdm with a dilution of dd, and non-caramelized diluted cats are dmdm with a dilution of dd.
You are very unlikely to see a caramelized cat in the wild, just like it’s unlikely to see a cinnamon cat in the wild, but feel free to make your cats caramelized if you’d like. While this site does take genetics seriously, it’s completely fine to have a cat that’s rare.
Chapter 4: The Agouti Gene
Vocabulary for this chapter:
- Agouti gene
- Ticked tabby
- Mackerel tabby
- Solid coat
- Classic tabby
- Tabby modifiers
- Spotted tabby
The agouti gene is what produces tabbies of all kinds. Tabbies are cats with mottled or striped coats, due to two or more colors on each hair. There are three types of tabbies and four types of coat, all of which have different dominancies, just like the black factor.
Let’s let the agouti gene be represented by A, and the solid coat gene be represented by a, because the agouti gene is dominant to solid coats.
First of all is the ticked tabby. This tabby has spots all over, except for on its legs, face, and tail, where there are stripes. This is the most dominant coat type, and can be represented by Ta.
A tabby with this coat type would be represented by Aa’Ta, Aa’TaTa, AA’Ta or AA’TaTa. If the tabby has two of the Ta gene, it has less of the “barring”, or less stripes. This coat type can mask all other tabby coat types, so a genotype of AA’Ta’mc would be a ticked tabby carrying classic tabby.
Second is the mackerel tabby. This tabby is the one most are familiar with, with stripes all over its body. This coat type and the classic tabby are the most common tabbies to find in the wild. Let’s let the mackerel tabby be represented by Mc.
A tabby with this coat type would be represented by Aa’McMc, Aa’Mcmc, AA’McMc, or AA’Mcmc. The lowercase mc is how the classic tabby, the most recessive coat type, is represented.
Third is the solid coat. This is dominant over classic, but recessive to ticked and mackerel. It would simply be shown as aa. Red and cream solid coats are special, because they are never truly solid, even with the solid genes. They still have very slight markings of tabbies, called “ghost markings”.
Last, but not least, is the classic tabby. This tabby has more swirl-like patterns than stripes, and can show up in genotypes of AA’mcmc or Aa’mcmc. It is not correct to call these tabbies “marbled” tabbies.
Now, let’s get into tabby modifiers. Just like dilution modifiers, tabbies have modifiers too. You were probably wondering why I didn’t mention spotted tabbies, and that’s because spotted tabbies are a modifier to only the mackerel type of tabby.
Let’s let Sp represent spotted tabbies, and sp represent non-spotted mackerel tabbies. SpSp and Spsp would create a spotted tabby if the cat has the genes for a mackerel tabby already, and spsp would create a normal mackerel tabby.
I have also heard of an “outlining” gene that produces marbled and braided tabbies, but as I can’t find much research on this topic, I’ll be leaving it out. Do your own research on it if you wish.
By the way, tortoiseshells can be tabbies! They are referred to as torbies sometimes, and you can find pictures of them online by searching that word.
Chapter 5: White Coloration: White Spotting, Dominant White, and Albinism
Vocabulary for this chapter:
- White spotting
- Dominant white
The most common white coloration in cats is white spotting. Let’s let white spotting be represented by S and no white spotting be represented by s. White spotting is dominant, so white spotting can be seen in SS and Ss genotypes, while the ss genotype has no white spotting.
SS creates from 50% to 100% white spotting, and can create fully white cats. Fully white cats produced through this are not at additional risk for deafness.
Ss creates 50% or less white spotting, and cannot create fully white cats.
ss does not cause white spotting.
If the white touches the eyes, the cat can have blue eyes, but as stated before, fully white cats who have blue eyes due to the white spotting gene are not more likely to be deaf than usual.
The dominant white gene is what can cause deafness. Let’s let it be represented by W, and no whiteness be represented by w. Ww and WW are genotypes that produce the phenotype of fully white cats, while ww cats will have their original coat color. These cats can either have orange or blue eyes, and the blue-eyed cats are the ones at risk for deafness.
Cats who have full white spotting or dominant white still carry the coat color passed down by their parent, but it is masked by the white.
Albinistic cats are a different matter than white spotting and dominant white, as the gene for albinism is both recessive and very rare. There are two types of genes for albinism.
cc represents a “true albino” with red eyes.
c1c1 represents an albino with extremely little pigmentation, but enough to have blue eyes. They are dominant to cc albinistic cats, as far as I am aware.
CC, Cc, and Cc1 represent non albinistic cats. The latter two are carriers of red eyed albinism and blue eyed albinism respectively.
Chapter 6: Expanding on the Albinism Gene
Vocabulary for this chapter:
- Lynx points
The following three coat patterns are variations of the albinism gene, and the first two can be combined.
Pointing, or colorpointing, is shown best in Siamese cats. They are mostly white, but their legs, ears, face, and tail are colored, hence the name colorpointing. It is represented by cs, and is dominant to other forms of albinism but codominant to sepia. Tabbies with colorpointing are known as lynx points. Colorpoints can only have blue eyes.
Sepia is also dominant to all other forms of albinism, but codominant to colorpointing. It is when a cat has a light body, but is darker in the legs, ears, face, and tail. The color looks faded in places other than those. This is represented by cb. Sepia cats usually have orange eyes, but can have other colors too.
When a cat has the cs and cb genes, such as cscb or cbcs, it is known as a mink. Sepia and colorpointing are codominant to each other, which means they produce a whole new coloration when combined. A mink is effectively a combination of the two genes, looking darker than the colorpoint but lighter than the sepia. Minks can only have blue eyes.
Chapter 7: The Inhibitor Gene
Vocabulary for this chapter:
- Inhibitor gene
- Silver tabby
- Wide band gene
Silvering, or the inhibitor gene, makes the undercoat of cats lighter. The tips of the fur are still fully colored, but the undercoat has a lighter tint. Depending on the fur color, there are different terms for silvering in cats.
The inhibitor gene can be represented by I, and is dominant. i does not represent non-silvering, it represents golden, which we will get to in just a bit. If a cat has only one copy of the inhibitor gene, it should be written as I-, not Ii.
A brown tabby with the inhibitor gene is simply called a silver tabby. However, for different fur colors, there are different terms. A chocolate tabby with the inhibitor gene would be called a chocolate-silver tabby, and a blue tabby with the inhibitor gene would be called a blue-silver tabby.
Red and cream tabbies with the inhibitor gene are called cameos. These cats are the closest you can get to a truly solid coat red or cream cat.
If the cat is solid and has the inhibitor gene, it is called a smoke. This can be applied to literally any coat color, including tortoiseshells.
Next, let’s talk about the wide band gene, represented by Wb. This produces chinchillas and shaded silvers. WbWb produces a chinchilla, Wbwb produces a shaded silver, and wbwb produces a normal silver. Chinchillas are cats that only have coloration on the very tips of their fur, and shaded silvers have less coloration on the fur than normal silvers.
Now, let’s get to the golden gene, which is recessive to the inhibitor gene. It is represented by i. This is also affected by the wide band gene. WbWb produces a chinchilla, Wbwb produces a shaded golden, and wbwb produces a normal colored cat. This is why, for simplicity’s sake, instead of writing out “ii wbwb” when you write out genotypes for each cat without the inhibitor gene, we simply skip that section for cats without the inhibitor gene.
Chapter 8: Fur Texture and Length
Vocabulary for this chapter:
- Short fur
- Long fur
- Curly fur
Fur length in cats is very simple. Short fur is represented by L, and is dominant, while long fur is represented by l, and is recessive. LL and Ll will produce short furred cats, and ll will produce long furred cats.
Fur texture is similar, and there are many genes for it. It can be either dominant or recessive to normal fur. For dominant fur types, such as the Russian Hairless, I’d write out Hp- instead of Hrhr, and for recessive fur types, such as the French Hairless, a cat would need two genes for it to be expressed, such as hh. However, if the cat was just carrying the gene, I would write out -h.
For hairless cats, there are:
The Russian Hairless, represented by Hp. HpHp and Hp- would produce a Russian Hairless. Dominant.
The British Hairless, represented by hd. hdhd would produce a British Hairless. Recessive.
The French Hairless, represented by h. hh would produce a French Hairless. Recessive.
The Canadian Sphynx, represented by hr. hrh would produce a Canadian Sphynx. Recessive.
For curly furred cats, there are:
The Selkirk Rex, represented by Se. SeSe and Se- would produce a Selkirk Rex. Dominant.
The LaPerm, represented by Lp. LpLp and Lp- would produce a LaPerm. Dominant.
The Devon Rex, represented by re. rere would produce a Devon Rex. Recessive.
The Cornish Rex, represented by r. rr would produce a Cornish rex. Recessive.
There is also the Wirehair, represented by Wh. WhWh and Wh- would produce a Wirehair. Dominant.
Chapter 9: Genetic Mutations
Genetic mutations range from harmless to deadly, and are much more likely within incestual litters. Some of the below are very harmful to cats, so it may not be advised to give your warrior cat them, as it may stop them from being able to be a warrior.
Paw and limb effects:
A gene that causes cats to have extra toes, or have “thumbs”. No harmful effects. Represented by Pd. Dominant.
A gene that causes cats to have lobster claw-like paws. No harmful effects. Represented by Sh. Dominant.
A gene that causes very short legs. No harmful effects shown with one copy of the gene, but with two, the spine is shortened to an extent that all kits with MkMk will be stillborn. Not recommended for warrior cat OCs. Represented by Mk. Dominant.
A gene that causes cats’ ears to curl backwards near the tip. No harmful effects, as far as I am aware. Represented by Cu. Dominant.
A gene that causes cats’ ears to fold forward, hence the name. This gene can cause stillborn kits, bone and cartilage disorders, and dwarfed body structure. Cats of this breed are usually in extreme pain, and are often put down due to this. Not recommended for warrior cat OCs. Represented by Fd. Dominant.
A gene that causes a lack of a tail or a stub tail. One copy of the gene can cause bone defects and organ defects, while two copies of the gene cause stillborn kittens almost 100 percent of the time. Not recommended for warrior cat OCs. Represented by M. Dominant.
A combination of genes that causes a curled tail in cats. No harmful effects. The dominant gene, Ae, causes an aerial tail, which is a thicker than average tail that tends to stick up while in the rest position. This, combined with two copies of the recessive gene rg, causes a ringtail.
A gene that causes cats to only have a stump for a tail. Unlike the Manx, no harmful effects are known. Represented by jb. Recessive.
A gene that causes two eyes of different colors. No harmful effects, although a white cat with one blue eye and one amber eye will likely be deaf on the side with the blue eye.
This only shows up in cats with Ss, SS, Ww, or WW genotypes, so there needs to be at least some white spotting for a cat to be heterochromatic. This is because those genes can stop pigmentation from reaching an eye during the development of pigmentation in eyes that all cats go through at around three months.
Before we begin, I just want to clarify that “O” means a lack of a chromosome. This is only a very small amount of the intersex conditions out there. Do your own research on those not mentioned here.
XO, or Turner’s Syndrome:
Most of these cats die before birth, but if they are born, they are infertile and have a small stature.
Does not develop, as many important genes are carried by the X chromosome, such as coloration.
XXX, or Triplo-X:
Some are normal females that are fertile, some are sterile females. Most have a large stature.
XXY, or Klinefelter Syndrome:
Feminine appearance despite being male, sterile. They tend to be large. This is where male torties come in, and this is the only way a male can be a tortoiseshell aside from chimeras.
XYY, or Jacob’s Syndrome:
Rare. Tall, fertile. Female.
Chapter 10: Resources
The best has been saved for last. While this guide may be very incomplete, there are more complete guides out there. Here are the links to some.
messybeast.com/catarchive.htm The best guide to cat genetics out there.
sparrows-garden.com/advanced-cat-coat-calculator/ A coat generator. Put in two parents, and possibilities for kittens are shown. There is also a simpler version on the site, but I recommend this one.
The books "Robinson's Genetics for Cat Breeders and Veterinarians" by Roy Robinson and "Cats Are Not Peas: A Calico History to Genetics" by Laura Gould are books on the subject that may interest you, although they are fairly expensive.