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The Color-Inhibitor Gene The first of the color-conformation genes controlling color expression is the color-inhibitor gene. This gene controls the expression of color within the hair and comes in two alleles: the non-inhibitor, "i", and the inhibitor, "Y".
The non-inhibitor allele, "i", is wild, is recessive, and allows expression of the color throughout the length of the hair, producing a normally colored coat.
The inhibitor allele, "I", is mutant, is dominant, and inhibits expression of the color over a portion of the hair.
The inhibitor allele is variably-expressed. When slightly expressed, the short down hairs (underfur) are merely tipped with color, while the longer guard and awn hairs are clear for about the first quarter of their lengths: the coat is said to be smoked. When moderately expressed, the down hairs are completely clear and the longer hairs are clear for about half their lengths: the coat is shaded. When heavily expressed, the down hairs are completely clear and the longer hairs are clear for about three-quarters (or more) of their lengths: the coat is then tipped or chinchilla.
Neither allele has anything to do with the actual color or pattern, only with whether that color is laid upon a clear undercoat or one of the beige ground color.
The Spotting Gene The next gene controlling color expression is the white-spotting gene. This gene controls the presence and pattern of white masking the normal coat pattern, and has four alleles: non-spotted, "s", spotted, "S", particolor, "Sp", and Birman, "sb". The presence of the parti- color and Birman alleles of this gene are still subject to argument at this time: their effect is not.The non-spotted allele, "s", is wild, is recessive, and produces a normal coat without white.
The spotted allele, "S", is mutant, is dominant, and produces white spotting which masks the true coat color in the affected area. This is a variably-expressed allele with a very wide expression range: From a black cat with one white hair to a white cat with one black hair.
The particolor allele, "Sp", if it exists, is a variation of the spotted allele affecting the pattern of white. The classic particolor pattern is an inverted white "V" starting in the center of the forehead and passing through the centers of the eyes. The chin, chest, belly, legs and feet are white. Variable expressions of this allele range downward to a simple white locket or a white spot on the forehead.
The Birman allele, "Sb", if it exists, is a variation of the spotted allele producing white feet. Variable expression ranges from white legs and feet to white toes only.
Unlike the white gene or the albinism gene, the white-spotting gene does not affect eye color: if your all white cat has green eyes, it is most definitely a colored cat with one big white spot all over.
The Dominant-White Gene The final gene controlling color expression is the dominant-white gene. This gene determines whether the coat is solid white or not, and comes in three alleles: non-white, "w", white, "W", and van, "Wv". The existence of the van allele is open to argument: it may be a separate gene.
The non-white allele, "w", is wild, is recessive, and allows full expression of the coat color and pattern.
The white allele, "W", is mutant, is dominant, and produces a translucent all-white coat with either orange or pale blue. Blue-eyed dominant-white cats are often deaf, orange-eyed cats occasionally so. Interestingly, a white cat may be odd-eyed, having one blue and one orange eye. Such a cat is often deaf on the blue side.
The van allele, "Wv", if it exists, is a variation of the white allele allowing color in the classic van pattern: on the crown of the head (often a two small half-caps separated by a thin white line), on the ears, and on the tail. Variable expression controls cap size and shape and the presence of color on the ears and tail. Occasionally, the caps will be missing and only the ears and/or tail will be colored.
It is important to remember that, genetically speaking, white is not a color, but rather the suppression of the pigment that would normally be present. A heterozygous white cat can an often does produce colored kittens, sometimes with no white at all.
Polygenes The genes described above control color and coat, and several breed- specific body features, but what about the genes that control the body structure itself? Can we not develop a cat with long floppy ears (sort of a bassett-cat)? The answer is a qualified no. Not within the realms of normal breeding, and not without a much better means of genetic engineering than is currently available to us. The reason cats (and horses) resist major changes, whereas dogs do not, is because the genes controlling these features are scattered among the genetic codes of other genes (remember, a gene is not a physical entity but rather a series of instructions). This type of scattered gene is called a "polygene". Polygenes are in firm control of many of those things that define the cat, and breeding programs can only change these characteristics slowly, bit-by-bit.
The Eye Colors There are no specific genes for the eye colors. Rather, the color of the eyes is intimately linked to the color and pattern of the coat via several polygenes.
There is much about eye color that is not yet understood. As an example, the British Blue usually has orange or copper eyes while those of the Russian Blue are usually green, in spite of the fact that the breeds have identical coat genotypes.
The range of eye color is from a deep copper-orange through yellow to green. The blue and pink eyed cats are partial or full albinos, with suppression of the eye color.
Color Abr Description Copper cpr Deep copper-orange Orange org Bright orange Amber amb Yellow-orange Yellow yel Yellow Gold gld Dark yellow with hint of green Hazel hzl Dark greenish-yellow Green grn Green Turquoise trq Bluish-green (common in Tonkinese) Siamese Blue sbl Royal Blue to medium-pale grayish-blue Dominant-White Blue wbl Medium blue Dominant-White Odd odd One blue, one orange Albino Blue abl Very pale blue, almost gray Albino Pink pnk Pink There is a definite interaction between the color genes, "B", "b", and "bl", the color density genes, "D" and "d", and eye color. This interaction is especially evident in those cats with Siamese coats where the eye color can range from a strikingly deep, rich blue for a Seal Point coat to a medium-pale, grayish blue for a lilac point coat.
Naming the Colors When it came to naming the colors, those who did so were firm believers in using the thesaurus: never call a color brown when you can call it chocolate or cinnamon.
The colors naturally fall into distinct groups: the "standard" colors, the shaded colors, the "exotic" colors, the oriental colors, and the whites. Each group may then be subdivided into several distinct smaller groups, each with a common characteristic. Each color name is followed by its karyotype in three groups (as they were discussed above), and the usual eye colors. Bear in mind that all possible combinations of color and pattern will eventually be realized, but not necessarily recognized: especially by the various cat fancies.
The Standard Solid Colors The solids form the basis for all other colors in nomenclature and karyotypes: these are the fundamental rendition of the eight basic coat colors. Solids are called "selfs" in Britain.
The black solid technically has a brown undercoat, but selective breeding has managed to eliminate the brown undercoat and has produced cats that are "black to the bone."
The subtle differences possible in blues (grays) has made this one of the most popular colors among breeders, with several breeds being exclusively blue. Blues, regardless of pattern, are often referred to as "dilutes."
The terms "chestnut" and "chocolate" are synonymous, as are the terms "lavender" and "lilac."
Since the orange allele of the orange-making gene also masks the non- agouti allele of the agouti gene, red and cream solids are genetically identical to red and cream tabbies. Careful selective breeding has made cause the non-agouti areas (the stripes) to widen and overlap, effectively canceling the paler agouti background and obscuring the tabby pattern. A generation or two of random breeding, however, and the stripes will return.
The patched solids, solid-and-whites or bi-colors, are formed by adding the white-spotting gene, "S*", to the solids. If, instead of the normal random white spotting gene, the particolor gene, "Sp*", is present, then the coat will show white in the particolor pattern. If both the random white-spotting and particolor genes, "SSp", are present, then a composite pattern will be evident. If the Birman gene, "sbsb", is present, then the pattern will be white feet only.
The tortoiseshells or torties are formed by combining both the dominant and recessive sex-linked orange genes, "Oo", with the solids. Because of the sex-linking of the orange genes, the tortie is always female. A tabby pattern may be visible in the orange areas, with any tabby pattern being permitted. In some individuals, the agouti and non-agouti orange areas may offer such contrast as to produce a false tri-color (black-orange-cream).
The patched tortoiseshells or calicos are formed by combining both the dominant and recessive sex-linked orange-making genes, "Oo", to the solids and adding the white-spotting gene, "S*". Like the torties, the calicos are always female, and like the patches, any white- spotting pattern is permitted.
Color Karyotype Usual eye color Black B*ooD* C*aa** iissww cpr org grn Blue B*oodd C*aa** iissww cpr org grn Chestnut b*ooD* C*aa** iissww cpr org Lavender b*oodd C*aa** iissww cpr org gld Cinnamon blblooD* C*aa** iissww org Fawn blbloodd C*aa** iissww org gld Red **OOD* C***T* iissww cpr org Cream **OOdd C***T* iissww cpr org
Black patch B*ooD* C*aa** iiS*ww cpr org grn blue patch B*oodd C*aa** iiS*ww cpr org grn chestnut patch b*ooD* C*aa** iiS*ww cpr org lavender patch b*oodd C*aa** iiS*ww cpr org grn cinnamon patch blblooD* C*aa** iiS*ww org fawn patch blbloodd C*aa** iiS*ww org grn red patch **OOD* C***T* iiS*ww cpr org cream patch **OOdd C***T* iiS*ww cpr org
The Standard Tabby Colors The tabbies are formed by adding the agouti gene, "A*", to the solids. This causes the otherwise solid color to show the pattern dictated by the tabby gene: light and dark stripes (mackerel allele, "T*") or blotches (blotched allele, "tbtb").
The brown tabby corresponds to the black solid: sufficient undercoat color shows in the agouti areas to provide a brownish cast. When in mackerel pattern, this is the "all wild" genotype, and represents the natural state of the cat.
The red tabby, when in mackerel pattern, presents an alternate stable coat often found on feral domestic cats, usually as a pale ginger.
The patched tabbies or tabby-and-whites are formed by adding the white spotting gene, "S*", to the tabbies. Like the patched solids, any white spotting pattern is permitted.
The tabby-tortoiseshells or torbies are formed by combining both the dominant and recessive sex-linked orange genes, "Oo", with the tabbies colors. Like the torties, the torbies are always female.
Color Karyotype Usual eye color tortie B*OoD* C*aaT* iissww cpr org blue tortie B*Oodd C*aaT* iissww cpr org grn chestnut tortie b*OoD* C*aaT* iissww cpr org lavender tortie b*Oodd C*aaT* iissww cpr org grn cinnamon tortie blblOoD* C*aaT* iissww org fawn tortie blblOodd C*aaT* iissww org grn calico B*OoD* C*aaT* iiS*ww cpr org blue calico B*Oodd C*aaT* iiS*ww cpr org grn chestnut calico b*OoD* C*aaT* iiS*ww cpr org lavender calico b*Oodd C*aaT* iiS*ww cpr org grn cinnamon calico blblOoD* C*aaT* iiS*ww org fawn calico blblOodd C*aaT* iiS*ww org grn brown tabby B*ooD* C*A*T* iissww cpr org yel hzl blue tabby B*oodd C*A*T* iissww cpr org yel hzl chestnut tabby b*ooD* C*A*T* iissww cpr org yel hzl lavender tabby b*oodd C*A*T* iissww cpr org yel hzl cinnamon tabby blblooD* C*A*T* iissww org yel hzl fawn tabby blbloodd C*A*T* iissww org yel hzl red tabby **OOD* C***T* iissww cpr org yel hzl cream tabby **OOdd C***T* iissww cpr org yel hzl brown patched tabby B*ooD* C*A*T* iiS*ww cpr org yel hzl blue patched tabby B*oodd C*A*T* iiS*ww cpr org yel hzl chestnut patched tabby b*ooD* C*A*T* iiS*ww cpr org yel hzl lavender patched tabby b*oodd C*A*T* iiS*ww cpr org yel hzl cinnamon patched tabby blblooD* C*A*T* iiS*ww org yel hzl fawn patched tabby blbloodd C*A*T* iiS*ww org yel hzl red patched tabby **OOD* C***T* iiS*ww cpr org yel hzl cream patched tabby **OOdd C***T* iiS*ww cpr org yel hzl torbie B*OoD* C*A*T* iissww cpr org yel hzl blue torbie B*Oodd C*A*T* iissww cpr org yel hzl chestnut torbie b*OoD* C*A*T* iissww cpr org yel hzl lavender torbie b*Oodd C*A*T* iissww cpr org yel hzl cinnamon torbie blblOoD* C*A*T* iissww org yel hzl fawn torbie blblOodd C*A*T* iissww org yel hzl torbico B*OoD* C*A*T* iiS*ww cpr org yel hzl blue torbico B*Oodd C*A*T* iiS*ww cpr org yel hzl chestnut torbico b*OoD* C*A*T* iiS*ww cpr org yel hzl lavender torbico b*Oodd C*A*T* iiS*ww cpr org yel hzl cinnamon torbico blblOoD* C*A*T* iiS*ww org yel hzl fawn torbico blblOodd C*A*T* iiS*ww org yel hzl The patched tabby-tortoiseshells, or patched torbies or torbicos, are formed by combining the dominant and recessive orange-making genes, "Oo", with the standard tabbies and adding the white spotting gene, "S*", to the torbie colors. Like the patched solids, any white- spotting pattern is permitted.
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