Cat coat genetics

This cat's coat allows it to blend in well with its environment

The genetics of cat coat coloration, pattern, length (short, medium or long), and texture is a complex subject, and many different genes are involved.

Cat coat patterns and colors

Cat coat genetics can produce a variety of colors and coat patterns. These are physical properties and should not be confused with a breed of cat. Furthermore, cats may show the color and/or pattern particular to a certain breed without actually being of that breed. For example, cats may have point coloration, but not be Siamese.

Blue (grey) and white bicolor cat
Bicolor, Tuxedo, and Van 
This pattern varies between the tuxedo cat which is mostly black with a white chest, and possibly markings on the face and paws/legs, all the way to the Van pattern (so named after the Lake Van area in Turkey, which gave rise to the Turkish Van breed), where the only colored parts of the cat are the tail (usually including the base of the tail proper), and the top of the head (often including the ears). There are several other terms for amounts of white between these two extremes, such as Harlequin. Bicolor cats can have as their primary (non-white) color black, red, any dilution thereof, and tortoiseshell (see below for definition).
Mackerel tabby, showing the characteristic "M" on its forehead.
Tabby 
Striped, with a variety of patterns. The classic blotched tabby (or marbled) pattern is the most common and consists of butterflies and bullseyes. The mackerel or striped tabby is a series of vertical stripes down the cat's side (resembling the fish). This pattern broken into spots is referred to as a spotted tabby. In addition, the individual hairs in a tabby-patterned coat may be banded with different colors, hence a "ticked" tabby. The worldwide evolution of the cat means that certain types of tabby are associated with certain countries; for instance, blotched tabbies are quite rare outside NW Europe, where they are the most common type.
Female tortoiseshell-and-white cat
Tortoiseshell and calico
This cat is also known as a calimanco cat or clouded tiger cat, and by the abbreviation 'tortie'. In the cat fancy, a tortoiseshell cat is patched over with red (or its dilute form, cream) and black (or its dilute blue) mottled throughout the coat. Additionally, the cat may have white spots in its fur, which make it a 'tortoiseshell and white' cat; if there is a significant amount of white in the fur and the red and black colors form a patchwork rather than a mottled aspect, in North America the cat will be called a calico. All calicos are tortoiseshell (as they carry both black and red), but not all tortoiseshells are calicos (which requires a significant amount of white in the fur and patching rather than mottling of the colors). The calico is also sometimes called a tricolor cat. The Japanese refer to this pattern as mi-ke (meaning "triple fur"), while the Dutch call these cats lapjeskat (meaning "patches cat"). A true tricolor must consist of three colors: a reddish color, dark or light; white; and one other color, typically a brown, black, or blue.[1] Both tortoiseshell and calico cats are typically female because the coat pattern is the result of differential X chromosome inactivation in females (which, as with all normal female mammals, have two X chromosomes). Conversely, cats where the overall color is ginger (orange) are commonly male (roughly in a 3:1 ratio). In a litter sired by a ginger tom, the females will be tortoiseshell or ginger. Male tortoiseshells can occur as a result of chromosomal abnormalities (often linked to sterility) or by a phenomenon known as mosaicism, where two early stage embryos are merged into a single kitten.
Siamese cat, classical colorpoint pattern
Colorpoint
The colorpoint pattern is most commonly associated with Siamese cats, but may also appear in any domesticated cat. A colorpointed cat has dark colors on the face, ears, feet, and tail, with a lighter version of the same color on the rest of the body, and possibly some white. The exact name of the colorpoint pattern depends on the actual color, so there are seal points (dark brown), chocolate points (warm lighter brown), blue points (dark gray), lilac or frost points (silvery gray-pink), red or flame points (orange), and tortie (tortoiseshell mottling) points, among others. This pattern is the result of a temperature sensitive mutation in one of the enzymes in the metabolic pathway from tyrosine to pigment, such as melanin; thus, little or no pigment is produced except in the extremities or points where the skin is slightly cooler. For this reason, colorpointed cats tend to darken with age as bodily temperature drops; also, the fur over a significant injury may sometimes darken or lighten as a result of temperature change.
The tyrosine pathway also produces neurotransmitters, thus mutations in the early parts of that pathway may affect not only pigment, but also neurological development. This results in a higher frequency of cross-eyes among colorpointed cats, as well as the high frequency of cross-eyes in white tigers.
White cats
White cat
True albinism (a mutation of the tyrosinase gene) is quite rare in cats. Much more common is the appearance of white coat color that is caused by a lack of melanocytes in the skin. A higher frequency of deafness in white cats is due to a reduction in the population and survival of melanoblast stem cells, which in addition to creating pigment-producing cells, develop into a variety of neurological cell types. White cats with one or two blue eyes have a particularly high likelihood of being deaf.
Smoke cats
The bottom eighth of each hair is white or creamy-white, with the rest of the hair being a solid color. Genetically this color is a non-agouti cat with the dominant inhibitor gene; a non-agouti version of the silver tabby. Smoke cats will look solid colored until they move, when the white undercoat becomes apparent. It is mostly found in pedigreed cats (especially longhair breeds) but also present in some domestic long-haired cats.

Genes involved in albinism, dominant white, and white spotting

The temperature sensitive albino genotype cscs produces point coloration at body extremities where lower temperature allows the mutated tyrosinase enzyme to become active.

Genes involved in red, black, brown, and diluted colors

A female domestic shorthair tortoiseshell cat.
This probably male cat shows the "red" O- genotype, with ll for long hair (though not show-quality), ss for absence of white spotting, and at least one Mc gene for the mackerel tabby pattern
A female Calico cat.

A cat with Oo and white spotting genes is commonly called a calico. The reason for the patchwork effect in female cats heterozygous for the O gene (Oo) is X-inactivation – one or the other X chromosome in every cell in the embryo is randomly inactivated (see Barr body), and the gene in the other X chromosome is expressed.

For a cat to be tortoiseshell, calico, or one of the variants such as blue-cream or chocolate tortoiseshell, the cat must simultaneously express two alleles, O and o, which are located on the X chromosome. Males normally cannot do this, as they have only one X chromosome, and therefore only one allele, and so calico cats are normally only female. Male tortoiseshell or calico cats occur only if they have chromosomal abnormalities such as the genotype XXY (in which case they are sterile), chromosomal mosaicism (only portions of their cells have the genotype XXY, so these cats may be fertile), or chimerism (a single individual formed from two fused embryos, at least one of which was male). Approximately 1 in 3,000 calico/tortoiseshell cats are male.[4] Chimericism (which may result in fertile male cats) appears to be the most common mechanism.

Genes

One can deduce that a grey male cat with a white bib and paws, but showing no tabby pattern:

Genes involved in fur pattern and shading

A mackerel tabby with the classic "M" on forehead.
An orange tabby with facial markings and nose spot.
The recessive mutant gene mc produces the blotched or classic tabby pattern.
A Brown Mackerel tabby cat with pencil lines on the face.
A tabby point on a Mekong bobtail.

Tabby cats

Tabby cats (AA or Aa), normally have:

Most or all striping disappears in the chinchilla or shaded cat, but it is still possible to identify the cat as a tabby from these other features.

The genetics involved in producing the ideal tabby, tipped, shaded, or smoke cat is complex. Not only are there many interacting genes, but genes sometimes do not express themselves fully, or conflict with one another. For example, the melanin inhibitor gene sometimes does a poor job blocking pigment, resulting in an excessively gray undercoat, or in tarnishing (yellowish or rusty fur).

Likewise, poorly-expressed non-agouti or over-expression of melanin inhibitor will cause a pale, washed out black smoke. Various polygenes (sets of related genes), epigenetic factors, or modifier genes, as yet unidentified, are believed to result in different phenotypes of coloration, some deemed more desirable than others by fanciers.

Tipped or shaded cats

Here are the genetic influences on tipped or shaded cats:

Genes involved in fur length and texture

Cat fur length is governed by the Long hair gene in which the dominant form, L, codes for short hair, and the recessive l codes for long hair. In the longhaired cat, the transition from anagen (hair growth) to catagen (cessation of hair growth) is delayed due to this mutation. A rare recessive shorthair gene has been observed in some lines of Persian cat (silvers) where two longhaired parents have produced shorthaired offspring.

There have been many genes identified that result in unusual cat fur. These genes were discovered in random-bred cats and selected for. Some of the genes are in danger of going extinct because the cats are not sold beyond the region where the mutation originated or there is simply not enough demand for cats expressing the mutation.

In many breeds, coat gene mutations are unwelcome. An example is the rex allele which appeared in Maine Coons in the early 1990s. Rexes appeared in America, Germany and the UK, where one breeder caused consternation by calling them "Maine Waves". Two UK breeders did test mating which indicated that this was probably a new rex mutation and that it was recessive. The density of the hair was similar to normally coated Maine Coons, but consisted only of down type hairs with a normal down type helical curl, which varied as in normal down hairs. Whiskers were more curved, but not curly. Maine Coons do not have awn hairs, and after moulting, the rexes had a very thin coat.

Curly coated

There are various genes producing curly coated or "rex" cats. New types of rex pop up spontaneously in random-bred cats now and then. Here are some of the rex genes that breeders have selected for:

Hairlessness

There are also genes for hairlessness:

Some rex cats are prone to temporary hairlessness, known as baldness, during moulting.

Here are a few other genes resulting in unusual fur:

See also

References

  1. French, Barbara. "Torties, Calicos and Tricolor Cats". Fanciers.com. Retrieved 24 October 2005.
  2. 1 2 "Cat Colors FAQ: Cat Color Genetics". Fanciers.com. Retrieved 2014-08-11.
  3. "Feline Breeds, Domestic Cats and Color Patterns". Cats.about.com. Retrieved 2014-08-11.
  4. Spadafori, Gina. "Feline Fallacies". The Pet Connection. VeterinaryPartner.com. Retrieved 2008-07-03.
  5. Kaelin CB; Xu X; Hong LZ; David VA; McGowan KA; Schmidt-Küntzel A; Roelke ME; Pino J; Pontius J; Cooper GM; Manuel H; Swanson WF; Marker L; Harper CK; van Dyk A; Yue Bisong; Mullikin JC; Warren WC; Eizirik E; Kos L; O'Brien SJ; Barsh GS; Menotti-Raymond M (2012). "Specifying and Sustaining Pigmentation Patterns in Domestic and Wild Cats". Science. 337 (6101): 1536–1541. doi:10.1126/science.1220893. PMID 22997338.

External links

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