cat coat coloration, pattern, length, and texture is a complex
subject, and many different
Genes involved in albinism, dominant white, and white spotting
The dominant C gene and its recessive alleles determine whether a cat is
a complete albino (either pink-eyed or blue-eyed), a temperature sensitive
albino (Burmese, Siamese, or a blend known as Tonkinese), or a non-albino.
If a cat has the dominant C gene, then the cat is non-albino and the W gene
determines its color.
The white masking gene, W/w. The dominant allele masks all
other colors by preventing pigment producing cell migration to the skin
during embryologic development. In other words, the cat has a greatly
reduced number of melanocytes. A cat that is WW or Ww will be
white, no matter what other color genes it may have. A cat that is
(ww) will express normal pigmentation, and the O gene will determine
its color. Some cats with the W gene are deaf or have depigmentation of the
iris of one or both eyes, resulting in blue eye color.
The white spotting or piebald spotting gene, S/s,
which has variable expression, so that an SS cat has more extensive
white patching than an Ss cat. It is this gene that creates the
familiar white blaze across the face, a white bib, tuxedo pattern, or
dappled paws. This gene can turn a cat's eyes blue if the white spotting
occurs over the eyes. A hypothetical Sb allele ("gloving gene") causes the
mittens in Birman and Snowshoe breeds. Some researchers believe that there
are separate white spotting genes for distinct features, such as the white
locket that some cats have on their neck.
Genes involved in orange, black, brown, and diluted colors
The sex-linked orange gene, O, determines if there will be
orange fur. This gene only appears on the X chromosome. In cats with orange
fur, phaeomelanin (orange pigment) completely replaces eumelanin (black
For males, O results in orange fur, and o means that the B gene will
determine the color (the black or brown color may be broken up into patterns
if the cat has the agouti gene).
For females, OO results in orange fur, oo means that the B gene will
determine the color (patterns if the cat has the agouti gene), and Oo
results in a tortoiseshell cat, in which the B gene determines the color of
the dark patches. A cat with Oo and white spotting genes will be a calico.
The reason for the patchwork effect in female cats heterozygous for the O
gene (Oo) is "X chromosome inactivation" - one or the other X chromosome in
every cell in the embryo is randomly inactivated, and the gene in the other
X chromosome is expressed.
Rufous polygenes, as yet unidentified, that affect the richness of the
orange gene's expression.
For a cat to be tortoiseshell, calico, or one of the diluted variants such as
blue-cream, the cat must simultaneously express two
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
The browning gene B/b codes for tyrosinase related protein-1, an
enzyme involved in the metabolic pathway for eumelanin pigment production,
and in its dominant form, B, will produce black color. Recessive
variants are b, producing brown (or chocolate), and bl
producing light brown or cinnamon.
The Dense pigment gene, D/d, corresponds to the dilute
phenotype. When a cat has two of the recessive d alleles, black fur
becomes "blue" (actually gray), chocolate fur becomes lilac, cinnamon fur
becomes fawn, and orange fur becomes cream.
Dilution modifier gene, Dm, which caramelizes the dilute colors in its
homozygous form (Dm-). The existence of this phenomenon as a discrete gene
is acontroversial subject among feline enthusiasts.
There is also a theoretical "black modifier" gene, Bm, which in its
recessive form, bmbm, causes these cats to turn amber or light amber. This
gene could be more appropriately called "agouti modifier" and is probably
related to the extension locus (the melanocortin receptor) or its ligand,
the agouti signaling protein. This phenomenon was first identified in
Norwegian Forest Cats. Other forms of extension mutations have been seen
in many breeds (and domestic cats), resulting in unique forms of tabby
One can deduce that a grey male cat with a white bib and paws:
has the o variant of the orange gene on its only X chromosome
(because the grey color corresponds to black, not orange)
has at least one S variant of the white Spotting gene (because it
has the white bib and paws)
has two w genes (because it expresses a fur color)
has the dominant B gene (because its fur color is a shade of
black rather than brown)
has two d (dilute) genes (because its fur is grey, rather than
Genes involved in fur pattern and shading
tabby pattern gene, Mc/mc, which sets the basic pattern of
stripes that underlies the coat: the basic wild-type tabby gene, Mc,
produces what is called a mackerel striped tabby (stripes look like
thin fishbones and may break up into bars or spots); while a recessive
mutant, mc, produces a blotched or classic tabby pattern
(broad bands, whorls, and spirals of dark color on pale background usually
with bulls-eye or oyster pattern on flank.) The classic tabby pattern is
common in Great Britain and in lands that were once part of the British
tabby pattern genes such as Ta / ta, at
which locus a dominant mutation produces an Abyssinian ticked or
non-patterned agouti tabby, having virtually no stripes or bars. (This is
one type of unpatterned tabby; the other type of unpatterned tabby is the
tipped / shaded / smoke cat. See inhibited pigment gene, below.) The
dominant form of the Abyssinian gene masks out all other tabby patterns.
Other genes are theorized to be responsible for creating various type of
spotting patterns, many of which are variations on a basic mackeral or
classic pattern. There are also hypothetical genes which affect banding
frequency, width, and size.
gene, A/a which codes for agouti signaling protein. The dominant,
wild-type A causes the agouti shift phenomenon which causes hairs to
be black pigmented at the tips and orange pigmented at the roots (revealing
the underlying tabby pattern), while the recessive non-agouti or
"hypermelanistic" allele, a, prevents this shift in the pigmentation
pathway. In its homozygous form, aa, this results in black pigment
production throughout the growth cycle of the hair. Thus, the non-agouti
genotype (aa) masks or hides the tabby pattern (Mc and mc). The O gene is
also epistatic over the aa genotype. That is, the A to a
mutation does not have a discernable effect on red or cream colored cats,
resulting in these cats displaying tabby striping independent of their
genotype at this locus. This explains why you can usually see the tabby
pattern in the orange patches of tortoiseshell cats, but not in the black or
There is an interesting gene, not yet identified but believed to be
related to the agouti gene, in the Chausie breed, that produces
silver-tipped black fur similar to Abyssinian ticked fur. The "grizzled"
phenomenon is purported to have been inherited from the hybridization of
these cats to Jungle Cats.
The inhibited pigment gene, I/i. The homozygous dominant
allele (II) produces tipped hairs that are fully colored only at the
tip and have a white base. The homozygous recessive allele (ii), when
combined with the agouti gene, produces normal wildtype tabby coloration.
Some of these cats in which the agouti shift happens early in hair growth
are termed "golden" cats. The melanin inhibitor gene interacts with other
genes, especially the agouti gene, to produce various degrees of tipping,
ranging from tipped to silver shaded and silver tabby, to smoke.
How breeders can identify and separate tabby genes
Cats with tabby genes (AA or Aa) normally have:
M on forehead. (Does this disappear in ticked, shaded silver, and tipped
Thin pencil lines on face. (Does this disappear in ticked, shaded
silver, and tipped cats?)
Black "eyeliner" appearance and white or pale fur around eyeliner.
Pigmented lips and paws.
A pink nose outlined in darker pigment
Torso, leg, and tail banding. (Torso banding disappears in the ticked
Most or all banding disappears in the shaded shorthair, but you can still
deduce the tabby genes from the other features, such as the "eyeliner"
The genetics involved in producing the ideal tipped, shaded, or smoke cat is
complex. Not only are there dozens of 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. Here are the minimum genetic
requirements for a tipped or shaded cat to exist:
Genes (such as Ta) causing unstriped body type.
Genes affecting number and width of bands of color on each hair.
Hypothetical wide band gene(s). Without a wide undercoat, the cat
appears as a tabby.
Genes to clear up residual striping (hypothetical Chaos, Confusion,
Unconfused, Erase, and Roan).
Various polygenes (sets of related genes), epigenetic factors, or
modifier genes, as yet unidentified, believed to result in different degrees
of shading, some more desirable than others.
Genes involved in fur length and texture
Cat fur length is governed by the Long hair gene in which the dominant
L codes for short hair, and the recessive
l codes for long hair.
There are many genes resulting in unusual fur. These genes were discovered in
random-bred cats and selected for. Some of the genes are in danger of going
extinct because the breeders have not marketed their cats effectively, the cats
are not sold beyond the region where the mutation originated, or there is simply
not enough demand for the mutation.
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 select for:
rr = Cornish rex
rere = Devon rex
roro = Oregon rex (extinct?)
Se = Selkirk rex
There are also genes for hairlessness, which produce the French hairless cat
(genotype hh), the British hairless cat (genotype hdhd), and the Canadian
cat (genotype hrhr). Some rex cats are prone to temporary hairlessness,
known as baldness, during moulting.
Here are a few other genes resulting in unusual fur:
The Lp gene (dominant) results in LaPerm cats with silky single coats.
The Wh gene (dominant, possibly incomplete) results in Wirehair cats.
They have bent or crooked hair producing springy, crinkled, coarse fur.
The Yuc gene, or York Chocolate undercoat gene, results in cats with no