Cat Genetics 2.2: Glossary of Colour and Coat Genetics
Colour loci with genes and versions (alleles)
Solid Colour Phenotypes where Locus A is (a/a)
Tortoiseshell Phenotypes in females due to Locus O
Colorpoint Phenotypes of Locus C
Pattern (Tabby) Genes and Loci
Pattern (Tabby) Phenotypes. Needs to be Locus A: (A/A or A/a)
Silver, Golden Phenotypes of Inhibitor (I) Locus
Breed Specific Colours and Patterns
Colour loci with genes and versions (alleles)
Locus A (Agouti). Locus A represents the ASIP gene which codes for a small signaling protein needed for yellow pigment formation by the melanocytes, the pigment forming cells of the skin and hair.
The dominant version or allele (A) is the wild type version and allows yellow pigment (pheomelanin) synthesis. This gives the phenotype called Agouti.
The recessive allele (a) codes for an inactive protein. The (a/a) genotype blocks the synthesis of yellow pigment, allowing only black pigment synthesis, and gives the non-agouti phenotype. The dominant (A) version of Agouti allows Tabby pattern genes to be evident, i.e. is permissive to Tabby.
In contrast, a double recessive (a/a) genotype masks tabby patterns and results in a solid (self) coloration. Indeed, it is the (a/a) genotype from Locus A that produces a black cat: black bands on a black hair shaft and black stripes on a black background (i.e. black on black on black) gives a black cat, no matter what the Tabby genetics are. Interestingly, the signaling protein that is coded for by Locus A is active on the cell receptor protein of melanocytes that is coded for by Locus E.
Locus B (Brown). Locus B represents the TYRP1 gene, which codes for a protein that helps the Tyrosinase protein (see Locus C) to function properly. The dominant wild type version (B) allows normal pigment formation.
In the cat, there are two recessive versions of Locus B. The (b) allele, when homozygous (i.e. present in two copies, b/b), gives a brown coloration. The (b’) allele, when homozygous (b’/b’), gives a cinnamon coloration.
Locus C (Colorpoint). Locus C represents the Tyrosinase (TYR) gene which codes for the Tyrosinase protein. The Tyrosinase protein is a key enzyme in pigment synthesis by the melanocytes; when it is fully active (wild type, C allele), both yellow and black pigments are formed (subject to the permissive or restrictive effects of Locus A).
When the Tyrosinase gene is completely inactive (c/c recessive alleles), the animal cannot form pigment and is recessive white or albino. Compare this to the effects of Locus W that results in a white cat, this time with dominant genetics. Note that the recessive white (albino) genotype (a/a) of Locus C will hide (is epistatic to) all other colour genes.
The cat has several additional recessive versions (alleles) of Locus C that are partially active (or partially inactive if you wish), depending on the body temperature; these are the colorpoint alleles.
For the colorpoint alleles, the Tyrosinase enzyme is now more active at lower body temperatures (legs, tail, face) and less active at higher body temperatures (back and belly). The (cb) allele, when it is a double copy i.e. homozygote (cb/cb), gives the sepia coloration of the Burmese breed. The (cs) allele, when homozygote (cs/cs), gives the colorpoint coloration of the Siamese breed.
A double carrier animal (cb/cs) has a mink coloration and is called a Tonkinese. A Tonkinese animal will not breed true, therefore there is no Tonkinese breed. Recently an additional colorpoint allele (cm) has been identified in the Burmese breed and is responsible for the Mocha/Bangkok coloration.
Locus D (Dilution). Locus D represents the MLPH gene which codes for the melanophilin protein. The D locus has two versions (alleles), the dominant wild type allele (D), which allows even distribution of pigment within hair shafts, and the recessive (d) allele, which causes clumping of pigment within the hair shaft resulting in non-pigmented segments.
When the animal is double mutant (d/d), this gives a washed-out (dilution) effect for both yellow and black pigments. The D locus is epistatic to (i.e. has effects on) Locus A, Locus B, Locus C and Locus O.
Locus E (Extension). The MRC1 gene is found at Locus E and codes for a receptor protein on the surface of melanocytes that binds the signal protein from Locus A. This receptor protein instructs the melanocytes, via Locus C (Tyrosinase), to produce both yellow (pheomelanin) and black (eumelanin) pigments. The wild type dominant allele of Locus E, (E), is found in most breeds of cats. A recessive allele (ea) is found in the Norwegian Forest Cat and is responsible for the Amber coloration seen in this breed. Another recessive allele (er) is found in the Burmese and is responsible for the Russet coloration of this breed. An additional recessive allele (ec) is found in the Kurilian Bobtail breed and is responsible for the carnelian coloration.
Locus D-M (Dilution-Modifier). The (Dm) allele is dominant over the wild type (dm) allele. Dm is only active in the presence of (d/d) from Locus D. The D-M locus has not been characterized at the gene level.
Locus I (Inhibitor). The (I) allele which is responsible for the Silver phenotype is dominant over the wild type (i) allele. The Inhibitor locus has not been characterized at the gene level.
Locus O (Orange/Red). Although the phenotype resulting from Locus O is well described and the gene is known to be X chromosome linked, the Orange/Red gene itself has not yet been identified. The dominant O allele (XO or XO) forces yellow pigment (pheomelanin) formation at the expense of black pigment (eumelanin) formation. The recessive and wild type o allele (Xo or Xo) allows both yellow and black pigment formation. Random X-chromosome inactivation in the female can result in the Tortoiseshell patterning seen when a female cat is carrier of both XO and Xo versions of the gene.
Locus S. Locus S is associated with white spotting. Although white spotting is well described phenotypically in the cat, the complete genetics of white spotting in the cat is complex and not well understood. Locus S is more than likely polygenic and awaits further characterization. Some progress in understanding white spotting caused by Locus W has been achieved.
Locus W (Dominant White). The KIT gene at Locus W has the recessive wild type allele (w), the dominant white spotting allele (Ws), and the Dominant White allele (Wd). The Birman Gloving phenotype is an additional allele (wg) of Locus W, this time recessive to wild type. The KIT gene is expressed during embryonic development in the cell line that will give melanocytes. When this expression is disrupted, melanocytes do not populate the skin and hair bulbs properly. Note that no melanocytes means no pigment and a resulting white spot. The Dominant White (Wd) allele results in the formation of one giant white spot, i.e. a white cat due to dominant genetics (compare this to the albino cat caused by recessive genetics at Locus C). In addition, the Dominant White allele (Wd) of Locus W can be associated with deafness while the other alleles of the Locus W are not.
Solid Colour Phenotypes where Locus A is (a/a)
Black (Ebony, Seal) Locus A : (a/a), recessive genetics
Chocolate (Chestnut) Locus B: (b/b), recessive genetics
Cinnamon (Sorel) Locus B: (b’/b’), recessive genetics
Blue (Grey) Locus D: (d/d), recessive genetics
Lilac (Lavender) Locus B: (b/b), recessive genetics
Locus D: (d/d), recessive genetics
Fawn (Beige, Sable) Locus B: (b’/b’), recessive genetics
Locus D: (d/d), recessive genetics
Caramel (Taupe) Locus B: (b/b), recessive genetics
Locus D: (d/d), recessive genetics
Locus DM: (Dm/-), dominant genetics
Red (Orange, yellow, Marmalade, Ginger)
Locus O: (XO/XO) female, sex linked, X-chromosome inactivation
Locus O: (XO/Y) male, sex linked, dominant genetics
Cream (female) Locus O: (XO/XO), female, sex linked, X-chromosome inactivation
Locus D: (d/d), recessive genetics
Cream (male) Locus O: (XO/Y), male, sex linked
Locus D: (d/d), recessive genetics
Apricot (female) Locus O: (XO/XO), female, sex linked, X-chromosome inactivation
Locus D: (d/d), recessive genetics
Locus DM: (Dm/-), dominant genetics
Apricot (male) Locus O: (XO/Y), male, sex linked
Locus D: (d/d), recessive genetics
Locus DM: (Dm/-), dominant genetics
White (Dominant) Locus W: (Wd/-), (where (-) represents any allele), dominant genetics
White (recessive; albino) Locus C: (c/c), recessive genetics
Tortoiseshell Phenotypes in females due to Locus O
Tortoiseshell (Torti, Particolor) are sex linked colour patterns in the female cat are the result of the dominant (O) and the recessive (o) alleles at the Orange/Red locus: (XO/Xo). They are also the result of random X-chromosome inactivation during embryonic development in the XX (female) embryo.
Normal tortoiseshell Locus O: (XO/Xo), sex linked genetics
Chocolate tortoiseshell Locus O: (XO/Xo), sex linked genetics
Locus B: (b/b), recessive genetics
Cinnamon tortoiseshell Locus O: (XO/Xo), sex linked genetics
Locus B: (b’/b’), recessive genetics
Cream tortoiseshell Locus O: (XO/Xo), sex linked genetics
Locus D: (d/d), recessive genetics
Lilac tortoiseshell Locus O: (XO/Xo), sex linked genetics
Locus B: (b/b), recessive genetics
Locus D: (d/d), recessive genetics
Fawn tortoiseshell Locus O: (XO/Xo), sex linked genetics
Locus B: (b’/b’), recessive genetics
Locus D: (d/d), recessive genetics
Carmel tortoiseshell Locus O: (XO/Xo), sex linked genetics
Locus B: (b/b), recessive genetics
Locus D: (d/d), recessive genetics
Locus DM: (Dm/-), dominant genetics, (-) represents any allele
Colorpoint Phenotypes of Locus C
Colorpoint (Siamese) Locus C: (cs/cs), recessive genetics
Sepia (Burmese) Locus C: (cb/cb), recessive genetics
Mink (Tonkinese) Locus C: (cb/cs), recessive genetics
Mocha/Bankok (Burmese) Locus C: (cm/cm), recessive genetics
Albino Locus C: (c/c), recessive genetics
White Spotting Phenotypes
Mitts (white gloves). Locus W: (wg/wg), recessive genetics.
Tuxedo
Bicolor
Mask and Mantle
Cap and Saddle
Harlequin
Van
Calico, tricolor. Tortoiseshell with white spotting.
Point and white. Seen in Snowshoe and Ragdoll breeds
Pattern (Tabby) Genes and Loci
Tabby (Mc). A dominant mutation (Mc) in the Taqpep/Laeverin gene results in the Mackerel stripe dark pigment patterns reminiscent of tigers. A recessive allele (mc) at the same site, when in two copies i.e. homozygote (mc/mc) results in swirls of dark pigment seen in the Classic Tabby phenotype.
Spot (Sp). A dominant allele (Sp) results in spot patterns of pigmentation reminiscent of leopards, while the recessive allele (sp) does not give spots. The Spot phenotype requires that the cat has at least one (Mc) allele at the Tabby locus. The Spot locus has not been characterized at the molecular level and may be polygenic.
Ticked (Ta). The Ticked tabby allele (Ta) results from a dominant mutation in the DKK4 gene. The recessive allele (ta) allows Mackerel and Classic tabby expression. Ta will block the expression of (i.e. is epistatic to) other tabby patterns and will thus mask the stripes and swirls of the Tabby locus and the spots of the Spot locus. This is not complete however, and when Ticked is heterozygote (Ta/ta) there is some evidence of stripes from the other tabby patterns, especially on the legs, tail and face.
Wide Band (Wb). Wide Band is a modifier gene of Ticked. A dominate allele (Wb) widens the yellow band on the hair shaft while a recessive allele (wb) is wild type. Wide band requires a functional Agouti allele (A) from Locus A to be functional. Wide Band has not been characterized at the molecular level and is probably polygenic.
Pattern (Tabby) Phenotypes. Needs to be Locus A: (A/A or A/a)
Note that Tabby pattens can be found with all variations of basic colors involving Locus B, Locus C, Locus D, Locus E and Locus O.
Mackerel Tabby (Tiger) (Mc/Mc) or (Mc/mc)
Classic Tabby (mc/mc), (Blotched tabby, Oyster tabby)
Spotted Tabby (Sp/Sp) (Note: spotted gene not characterized)
Broken Tabby (Sp/sp) (Note: gene not characterized)
Ticked Tabby (Ta/Ta) or (Ta/ta), seen in Abyssinian
Wide band (Wb/Wb) or (Wb/wb) (Note: gene not characterized)
Silver, Golden Phenotypes of Inhibitor (I) Locus
The Inhibitor (I) locus gives shaded, tipped color varieties to cats. This is a modifier gene for Agouti (Locus A) and possibly for the Wide-Band locus. The Inhibitor gene is also called the Inhibited Pigment Gene and the Melanin Inhibitor Gene. A dominant (I) allele and a recessive wild type (i) allele are described. The dominant (I) allele causes melanin production to be suppressed, more for pheomelanins (yellows) than for eumelanins (blacks). For tabbies, the base of the hair becomes pale (silver) while the tip of the hair and the stripe color is not nearly as affected, giving a Silver tabby. For solid cats, the (I) allele causes the base of the hair to be pale to give Smoke (Silver Smoke). The Inhibitor gene has not been cloned nor characterized at the molecular level.
Silver tabby
Silver shaded
Smoke. Silver gene (I) on a solid background, i.e., on Locus A: (a/a). This is more apparent on longhaired cats with (I/I) at Locus L.
Smoke tabby. The Smoke phenotype on a short-haired cat, where Tabby patterns are somewhat more evident.
Golden. A variation of Silver due to the combining effects of Locus A, Locus D and Locus Wide band.
Cameo. The (I) allele on Locus O (Orange) cats.
Breed Specific Colours and Patterns
Ruddy. Reddish coloration seen in Abyssinian and Somali breeds.
Agouti tabby. Ticked tabby without banding on legs, tail neck.
Sepia agouti. Dark ticking on ivory background seen in the Singapura breed.
Amber. A shade of brown coloration seen in the Norwegian Forest Cat, due to a recessive allele (e) at the E locus. Kittens are born dark but their coloration lightens with age.
Russet. An additional shade of brown seen in the Burmese breed, due to a different recessive allele (er) at the E locus. Once again, kittens are born dark but their coloration lightens with age.
Nonagouti amber.
Sunshine. A type of Golden tabby seen in the Siberian breed. Silver sunshine cats are called bimetallics.
Grizzle. Variant of ticked pattern, seen in the Chausie breed, with silver tipped black fur similar to Abyssinian ticked fur.
Glitter. Seen in the Bengal breed. Similar to Grizzle for the Chausie.
Satin. Seen in the Tennessee Rex breed. Similar to Grizzle for the Chausie.
Mocha. Seen in the Burmese breed. Locus C recessive allele (cm) seen in the Burmese.
Coat Type Phenotypes
Long hair (Locus L). Four recessive mutations in the FGF5 gene can give long hair, as homozygous recessive or as double heterozygotes (carriers).
Cornish Rex curly coat. A recessive mutation in the LPAR6 gene.
Selkirk Rex curly coat. A dominant mutation in the KRT71 gene.
Sphynx (Canadian hairless). A recessive mutation in the KRT71 gene.
Devon Rex. A recessive mutation in the KRT71 gene.
Peterbald/Donskoy hairless. A dominant mutation.
Morphology
Short tail (Japanese bobtail). Recessive mutation in the HES7 gene.
Short tail (Manx). Three dominant mutations are identified in the T-box gene.
© 2022 David W. Silversides