Ok, folks. Some of you asked to see my information on genetics, so here you go. I take no responsibility for the headache that it's going to give you!

I'd ask that you please not copy or reproduce this without asking first.

So, your cat is pregnant. One of the most common questions people ask is what colour the kittens will be. This all comes down to genetics. I’ll start with the basics.

What is a gene?
In its simplest form, a gene is a part of your DNA. It is a chain of different molecules which code for the production of a protein in the body. These proteins and coding strands are responsible for many things from hair colour to height, skin tone and even weight to some extent (no, that can’t be used as a valid reason to go eat chocolate!). In short, genes are the things that make you look the way you do. They are passed to you from your mother and your father. In this article, I’ll be looking at genes specifically linked to coat colour and pattern.

How do we get genes?
At the point of fertilization, a sperm from the father and an egg from the mother join. Each of these cells carries genetic or DNA information which binds together when the cells join. DNA is housed on things called chromosomes. Most are x-shaped, one half being formed from the mother’s DNA and the other from the father’s. Genes therefore have a pair partner on the opposite strand of the chromosome. However, whereas a female possesses all X shaped chromosomes, a male has one in each cell that is a Y shape. It is missing a leg. This means that genes on the opposite corresponding leg have no pair partner. Cat coat colour genes exist on this chromosome, which explains why girls only are torties. Boys can only express one colour at a time due to not having a pair partner in the DNA for the colour gene. Those male torties that do exist are sterile. This is because they not only have an x-y chromosome as normal males do, but they have an XXY set-up, meaning they have an extra, unwanted chromosome. This has the added effect of making them sterile.

Dominant and Recessive
Genes come in two types. These are called dominant and recessive. Dominant genes do what their name suggests; they dominate. Just one dominant gene will mean that a cat exhibits the trait linked to that gene. Recessives cannot manifest alone. There needs to be two recessives in order for the physical trait to be noticed. To understand genes, you need to remember that they always come in pairs, one from the mother and one from the father. When it comes to coat colour, the recessive gene commonly seen is called a dilute gene. This is because it dilutes the true colour of the coat to form something else.

A person can be said to be a carrier of a recessive, but not a dominant. Why? Because carriers possess the gene, but do not show the physical trait. Remember, if a person, or a cat has a dominant gene, they will show that trait even if they only have one dominant. So, if they have a dominant, they cannot carry the gene because they show the trait. The same is true if they possess two recessives. However, if they have only one recessive, then they will possess the gene but not the trait, so can be called a carrier. This will be important when we come on to predicting colour possibilities in cats.

Speaking of cats, let’s get to colour. Believe it or not, there are only two true colours in cats. Despite the profusion of different coloured coats and combinations out there, they all come from only two colours. Those are black and red. Every coat colour’s genetics can be traced back to either black or red. But how? That’s what I’m going to try and explain. And that’s when it gets complicated.

Dilutes, the recessives remember, are very important in coat colour in cats, as they allow deviation from the blacks and reds. Black and red are dominant, but the dilutes, even though they are recessive, are able to work in tandem with this dominant to alter it. If a cat has the dominant gene for black, but also possesses two dilute genes, then instead of black, their coat will turn blue. Likewise, if another cat has the dominant for red, two dilutes will work with the red gene to produce a cream coat.

But you’ve seen cats that show black and red together, haven’t you? Or cats who show blue and cream? Well, that’s very common. These cats are called torties and blue torties/blue-creams. Most of them are female, but a very small percentage can be male. Females exhibit black and red or the dilute forms of them due to having two x chromosomes. So although the two are dominant, they can both exist in harmony given their position on chromosomes. If a boy had two x chromosomes, he could do the same thing.

So, by the logic we’ve already explored, you couldn’t have a cat with red and cream in its coat. Why? Because it takes two dilute genes to make cream, and if you have two dilutes, they cancel out the red. Similarly, you couldn’t have a cat with black and blue. The same is true when you look at red and blue or cream and black. I hope you understand why. Remember, two recessives/dilutes code for cream and blue, so when they’re there, they cancel out the red and black. Blue-cream exists together because both are dilute colours. Red and black exist together because both are dominant colours.

Chocolate and cineamon
Just to complicate things further, there’s another way that colours can vary. Well, there’s more than one, but let’s keep it simple. Chocolate is an alteration of the black dominant gene. So imagine a black gene with an extension which changes it to chocolate and you're close to understanding how it works. Chocolate, of course,can also be altered by a dilute. Confused? I was for a long time. Basically, chocolate acts like a recessive gene. That means, as with the dilute, that two copies of chocolate must exist before the cat can have a chocolate colour visible on its coat. One copy alone makes the cat a chocolate carrier. However, here’s where things get extra tricky. Chocolate can itself be modified by that old friend, the dilute. If a cat has two copies of chocolate and two dilutes, then it makes lilac. Obviously, if a cat only has one dilute then chocolate still wins. If it has only one chocolate, then the dilute will act on the dominant coat colour, red or black.

Ready for more complication? Chocolate cannot impact the red gene, so if you have a red boy or girl, they can have two copies of the chocolate gene and not show it. They can also have two copies of the dilute and still not show chocolate or lilac, although in this case, the base colour of the coat would be cream, not red (remember, red plus two dilutes =cream).

Now to come on to cineamon. Keeping it as simple as possible, cineamon is also an alteration of the black gene, but in order for cineamon to be expressed, then the chocolate extension to the black gene must already be in place. Thus, to have a chocolate cat, you must have the black gene. To have a cineamon coloured cat, you must have the chocolate extension or part of the black gene already there.

Then if you add in a dilute to that mix, a cineamon cat becomes a fawn.

White: Although this isn’t exactly a colour, it is almost like a trump card, for if copies of a white gene exist, they mask all other colours. So even if a cat possesses the genetic make-up to be a tortie, it will still appear white due to the masking properties of this gene. Even if only one copy exists, the cat will still be white. This is the ace of spades when it comes to colours!

So, to recap:
Black and red are dominant, so only one copy is necessary to see a physical trait presented.
Dilute is recessive. If only one copy exists, a cat is a dilute carrier. If two copies exist, black cats become blues, red cats become creams, and tortie cats become blue-creams
Chocolate acts like a recessive gene which only modifies the black dominant. Any reds with two copies of the chocolate gene will remain red but can be referred to as red chocolates. Two copies of the gene on a black cat will make it a chocolate. One copy will make any cat a chocolate carrier.
The dilute modifies chocolate, if two copies exist, to become lilac.
White is the trump gene, masking all other colours. Any cat with even one copy of the white gene will appear as all white. Any cat with two copies of the gene will consistently produce offspring who are all white.

Ok, now that we have that sorted, we do, don’t we? It’s time to move on to patterns.

Colourpoint is a recessive gene, so two copies are necessary for a cat to be pointed.
Tabby is a dominant, so only one copy is necessary for tabby to become the pattern.
Bicolour is also dominant. When one copy of the gene is present, a black cat becomes a black and white bicolour, a red cat a red and white bicolour, and a tortie a dominant tortie and white. Remember that with the influence of the dilute, you can also get blue and white bicolours and cream and white, as well as dilute tortie and white. If a cat has two copies of the gene, it will be mostly white and will be called a van.
Shaded/smoke/shell: This too is dominant. One copy alone makes a black cat a black smoke, a red cat a red smoke and a tortie a tortie smoke. The smoke gene varies in its expression though, producing something called variable penetrance. This basically deals with the length of the hair shaft that the colour extends to. Smokes have a hair shaft that is mostly coloured, but with a white undercoat. When the colour extends 50% down the shaft, the cat is a shaded rather than a smoke. Some cats have colour just on the tips of the shaft, and these are called shells.

There is one final pattern, silver/golden, but it is quite a complex one to explain given that it is a combination of three genes working together. If any of you wish to know more, please write me privately and I’ll direct you to an informative article to read.

Ok, now to colour prediction at last. There are two ways to do this. The first is to look at a cat’s pattern and work through it until you reduce the genes to the dominant red or black (remember, every pattern is made from these colours). This is called de-construction. The second way is to take the cat and begin with black or red, adding the modifier genes until you come up with the existing pattern. This is often what we breeders have to do to work out the possibilities for colour and pattern from specific matings. I will give you examples of each and talk you through how to do them. I’ll start with de-construction, as it’s probably a bit easier. I’ll concentrate on tabbies, colourpoints and bicolours as these are easier to get to grips with.

Deconstruction
1. A blue tabby. First of all, remove the tabby gene. This leaves you with a blue cat. Then remove the dilute to leave black.
2. A cream and white bicolour. Remove the bicolour to leave a cream, then remove the dilute to leave red.
3. A blue tortie colourpoint. Remove the colourpoint to leave a blue-cream tortie. Remove the dilute to leave tortie.
4. A white. Remove white to get… Anything is possible. Remember, white masks any colour or pattern combination.
5. A lilac tabby colourpoint. Remove the tabby to leave a lilac colourpoint. Remove the colourpoint to leave a lilac. Remove the chocolate to get blue. Remove blue to get black.

Construction.
1. A cream tabby. Add dilute to red to get cream. Add tabby to cream to get cream tabby.
2. A blue and white bicolour. Begin with black. Add dilute to get blue, then bicolour to get a blue and white bicolour.
3. A blue-cream tabby colourpoint. Begin with tortie, red and black. Add dilute to get blue-cream. Add tabby to get a blue-cream tabby. Add colourpoint to get a blue-cream tabby point (also called a blue tortie tabby point).
4. White. Start with black or red, and add anything you like. As long as you finish with adding white, the cat will appear white, no matter its genetic colouring or patterning.
5. A red chocolate colourpoint. (Remember, chocolate only modifies the black gene. This cat would actually be seen as a red colourpoint). Start with red. Add chocolate to get red chocolate (this will appear to the eye as still a red cat). Then add colourpoint to get a red choc colourpoint. Note: The cats would be classed by registering bodies as red colourpoints despite carrying two copies of the chocolate gene.

The challenge:
As a breeder or owner of a pregnant cat, you will need to be able to generate colour/pattern possibilities based on the pattern and colour of the mother and father. To this end, I am going to leave you with the colours and patterns involved in a specific mating. Try to predict the colours of kittens the mother might produce. Do remember though that torties or blue-creams are usually only female. Also remember that a tortie mother can pass on either black or red to her offspring, while the father can only pass on one colour.

The mother is a seal tortie colourpoint carrying dilute and chocolate. Seal is a modification of the black gene, but for the application of genetics, treat it as a black gene in your workings out. So in simple terms, she is a tortie colourpoint carrying dilute and chocolate. The father is a cream colourpoint who does not carry chocolate. So, what colour kittens will she produce? For the really enterprising among you, predict whether they will carry chocolate/dilute as well. I’ll tell you the answer at the end of the article.

To help you, I will outline the process involved in predicting offspring from a different mating combination.
Mother: blue tortie tabby carrying colourpoint.
Father: chocolate colourpoint. He does not carry dilute.

De-construction:
Mother: remove tabby to leave blue tortie, and dilute to leave tortie.
Father: Remove colourpoint to leave chocolate, and chocolate to leave black.

Combinations:
All kittens will carry dilute, as the mother has two copies and the dad has none. Therefore, blues, creams, lilacs, blue-creams or lilac-creams are not an option, because no kitten will get two copies of the dilute gene.
All kittens will carry colourpoint as the dad has two copies. Colourpoint kittens are a possibility if the mother passes on her single copy to offspring.
If the mother carries two tabby genes, all offspring will be tabby. I know this mother did not, which means tabby is a possibility as she only carries one copy of this dominant gene.
Girl kittens: black, black tabby, seal colourpoint, seal tabby colourpoint, tortie, tortie tabby, seal tortie colourpoint, seal tortie tabby colourpoint.
Boys: black, black tabby, seal colourpoint, seal tabby colourpoint, red, red tabby, red colourpoint, red tabby colourpoint.
Note that boys are not torties, and that boys can be solid red where girls cannot. This is because the father always passes a black gene. Girls, because of their x chromosomes can express both black and red at the same time, but for the boys, it is the mother who has the final say on colour, hence the ability for her red to be expressed. This is because it is the mother who passes on the X chromosome and the father the Y. Remember that the colour genes are on the leg of the chromosome missing from the y.

I hope this has been helpful, and sorry it’s been so long and confusing!

Answers:
From the above mating, you can expect to see the following:
All kittens will either show dilute colours of blue or cream, or will be dilute carriers.
Kittens may or may not be chocolate carriers, but there is no way to tell.
All kittens will be colourpoints.
Girls: red, cream, seal tortie, bluecream.
Boys: seal, blue, red, cream.

you are amazing!!!

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Wow!!!

Thank you, I think I understand most of it and was close at the end. Please can you just clarify why there are no blue girls?

I used a pen and paper and can show my workings.

I think you deserve a stiff virtual drink!!!

Never thought a forum post could make me blush! I'm glad it's been useful.

Hi CARLY,

you're mostly right but there are a few errors in there. I'll have another look at it later, got to go do dinner for the hungry hoardes! Genetics is my thing, feel free to ask any questions!




Dominant and Recessive
Genes come in two types.

Not true I'm afraid, many genes have a variety of possiblities called 'alleles' and many d onot show a simply domniant or recessive relationship. For example there are a whole spectrum of possiblities with some characteristics, its not matter of one or the other.



Chocolate
Just to complicate things further, there’s another way that colours can vary. Well, there’s more than one, but let’s keep it simple. Chocolate is an alteration of the black dominant gene.

Choclate is an allele of black, its a different form of the black gene, Cinnamon is another form of the black gene. Black is dominant to chocolate, which is dominant to cinnamon. There is no additional modifier gene involved.

Dilute is a separate gene to one of the pigment genes, it does the same thing to any pigment, i.e makes the pigmant more diffuse in the hair shafts.

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Emma Yeoman
Purindoors Birmans
www.Purindoors.co.uk

Hi there, Emma

Point taken on the chocolate. I'd copied this from an older version and hadn't realised.

As for dominants and recessives, I know there's more to it than that, but wanted to keep it as simple as possible for those just starting out in genetics.

I'll change the chocolate bit, but if you pick up on anything else, please let me know and I'll fix it.

Carly

Ok, I've changed the chocolate bit and included cineamon. Please remember, folks, that I'm trying to simplify a very complex subject, so go easy on me as I know I'm not using the correct terminology. My OCD is screaming at me to fix it, but I won't, as it makes it more difficult to understand.

In the courses I've written I use the analogy of a childs shape sorting toy.

Each chromosome is a shape sorting toy, there are 18 pairs of toys, and 1 not identical pair 0 the sex chromosomes.

Each 'gene' in each chromosome is a shaped hole in the toy, e..g round, triangle, square, star etc. So each cat will have 2 possible 'pegs' for each gene, they can be the same - homozygous, or different -heterozygous.

In the 'round' hole for the Eumelanin pigment there are 3 possible pegs, black, chocolate and cinnamon, all 3 are 'round' pegs ( produce eumelanin) BUT the shape of the grains of pigment are different - hence the percieved change in colour.


The 'star' shaped hole has pegs which code for the amount of pigment in each hair, e.g. dilute. So whatever colour is produced (Eumalanin for black, Phaeomelanin for red) the amount is determined by this gene.

Another 'hole' is where the genes for colourpoint sit, these are again an example of multiple 'pegs' fitting the same hole.
C is the allele in normal colouration and is dominant to all the others.
cs produces a colour point/Siamese pattern
cb is co-dominant with cs and produces a Burmese pattern
c is recessive to all other alleles can produces albinism.

The toy which holds the hole for the phaeomelanin gene is on the 2 dis similar chromosomes ( toys) the sex cells. there is only a slot on the X chromosome ( female has 2, male has 1).

The red gene is very strong, it forces hairs to produce phaeomelanin, this doesn't mean the original 'round' hole on the other choromosome is not filled with the black/choc/cinnamon peg, its still there just 'covered' by the red influence.

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Emma Yeoman
Purindoors Birmans
www.Purindoors.co.uk

See, this analogy confused me more because I ended up concentrating ondifferent shaped holes and not really understanding dominance issues. I guess it's different strokes for different folks. It's a great description!

Thanks for the post - and thankyou for putting it in laymans terms.

I had a quick skim through and kind of got the right answers - will go through it again properly and try again tomorrow.

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notsure