The Color of Aristocats: A Tale of Genetics!

White, black, chestnut, gray, blue or downright unlikely mixtures … A cat would not find her little ones!

The colors of cats are sometimes specific to a breed. Thus, all the Chartreux will present a coat with shades of gray-blue, which is simply called “blue”. Sacred Burma cats sport a golden beige fur, with the ears, legs, tail and part of the darker face (a mask). We are talking about a “Colourpoint” dress. Because yes, the different types of coat colors are called “dresses”.

However, overall, the color of this coat does not depend on a particular breed and the cats of different breeds can present more or less common dresses.
The dresses are therefore characterized by a set of distinct colors, with first a basic color.

In cats, there are 9 basic colors with very specific names. We find thus:

• White,
• Black,
• Blue,
• Chocolate (brown),
• The lilac (beige-ross),
• The cinnamon (brown-red),
• the faon (light beige going to the red),
• Roux,
• The cream,
• The chinchilla.

These colors are then distributed differently over the body, which creates specific patterns, specific to each dress.
For example, so -called “CARIICALS” cats have a coat mixing two basic colors.

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How are the artistochats's pelages color?

The pigmentation of artistochats, and more broadly mammals, is linked to the presence of particular cells, melanocytes. These pigment cells are found in precise places in the body. We observe of course in the skin: more precisely at the dermis, epidermis and hair follicles (hairs). But also at the eye level, especially to ensure the coloring of the retina.

Melanocytes contain very specific organelles: melanosomes. They contain two types of pigments: Eumelanines, with brown with black and pheomelanins, with yellow with red. It is a particular enzyme that allows their synthesis: tyrosinase.

The color of the coat will depend on the activity of these melanocytes, in particular those which are at the base of the hair follicles. When we say “activity”, we hear the type of pigment that will be made in these cells.
Thus, a cat with a color pulling on the “yellow” will have cells producing especially pheomelanin and not or little eumelanin. On the other hand, the black color betrays an almost exclusive synthesis of Eumelanine.

The synthesis or not of the pigments is genetically determined. More specifically, it is the MC 1R gene that code for a protein that controls the production of pigments.

>> Read also: skin pigmentation in Europe: a later and complex evolution than expected

When a gene is hidden … Many others!

Nothing is really so simple in genetics. For pigments, a gene comes into play, but for the determinism of colors … There is another story!

Already, we cannot really talk about gene, but locus. It is a specific place on a chromosome where one or more genes are expressed. Because yes, often, there is not only one gene that comes into play, but a whole combination. Otherwise, it would be too easy …

We have seen that there was a specific gene for the synthesis of the pigments, but it is other genes which ensure the distribution and the proportion of eumelanins and pheomelanins in the body of cats.
Thus, for the basic colors, 4 LOCIs come into play. These are Locus C (Colorpoints), Locus A (Agouti), Locus O (Orange) and Locus E (Extension).

These basic colors can then be modified by other genes. The brown gene (Locus B), leads to the accumulation of eumelanin, which gives black cats. On the other hand, the White (dominant white) gene makes it impossible to produce Eumelanine. The cat will then be all white. As for the Agouti gene, located on Locus A, it is essential for the production of pheomelanin. If it is active, the yellow pigment is formed. On the other hand, if it is inactive, the yellow pigment is not formed, but black can express themselves.

We can also cite other genes that will give patterns of very specific dresses, such as the Tabby gene. It will allow cats to obtain tiger dresses with long lines or speckled tigers.

Note that the genes are in two copies: one comes from the father, the other from the mother. A copy of this gene, which is called allele, perhaps dominant and preventing the other allele from expressing themselves. The latter is then said to be “recessive”. A cat can therefore have two dominant alleles, two recessive alleles or a mixture of the two (it will then very often be the dominant version which will be expressed). In addition, some genes interact with each other and can mask or “authorize” the expression of other genes …
In short, you will understand, the combinations for our Aristochats are impressive!

>> Read also: 101 Dalmatians and as many spots … Where do they come from?

And what about our aristochats?

It's all good, but let's go back to our matous. How can our Aristochats have different dresses? Or, to reformulate, how can a white pussy like Duchess give birth to three kittens of three different colors?
As a reminder, the three Duchess kittens are Toulouse, a red male, Berlioz, a black and Marie male, a white female. We don't know their father, so we don't know his color.

In this color story of Aristochats, we will be interested in the location of certain color genes, namely the chromosomes on which they are. And more particularly, we will be interested in sexual chromosomes, the famous X and Y.
A male cat receives a chromosome y from his father and a chromosome from his mother. A female kitten receives an X chromosome from her father and a mother's X chromosome. However, one of the decisive LOCIs for color, and which we have already talked about, is on sex chromosomes!

It's the famous Locus O (Orange)! It is on the X chromosome. This locus is specific to cats. It has two alleles: “o” determines the red color and “o” determines its absence. Thus males and female can be “red” (xo/y and xo/xo) or “non-roux” (xo/y and xo/xo). On the other hand, only females can present both red and non-roux hairs (XO/XO). This corresponds to the famous dress called “turtle scales”.

This dress results from a particular phenomenon, which is called “alternate inactivation of X chromosome”. During embryonic development, in mammalian females, one of the two X chromosomes is “extinct” randomly in each cell, by epigenetic mechanisms. This “extinction” therefore varies from one cell to another; Some will therefore have the XO “extinguished”, while for others it will be the “XO”. In melanocytes, which are cells, this random extinction will therefore lead to the expression of red or non -red hair beaches (often black).

>> Read also: Eye color: Little story of genetics

But Duchess is not “turtle scales” …

Duchess is most certainly carrying the two versions of the Orange locus on its X chromosomes. It is therefore XO/XO.

During the reproduction, she transmitted one of her two x to her kittens. Berlioz, the black kitten, most certainly received the XO version (“non-roux”), while Toulouse received the XO “Roux” version, hence their two different colors.
Okay … But Duchess is not “turtle scales”, she is white. Where is it confusion?

Previously, I told you about the White (W) gene that determines the white. However, this gene is dominant on all the others. A cat that therefore has the dominant allele W (homozygous: W/W or heterozygous W/W) will therefore be entirely white, whatever the other color genes. Duchess must therefore be W/W or W/W (since W is dominant on W), and also Marie.
On the other hand, the two male kittens must be recessive (W/W).

To summarize, the color of our 4 Aristochats is determined by a complex action of their genes …
Like what, the Disney cartoons make us heat the men'ses!

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