CAT GENES AND GENE SYMBOLS

This page simply lists the symbols for commonly referenced genes for colours, patterns and anomalies. Where there are several alleles, these are listed in order of dominance (some are co-dominant) though the order of dominance for posited genes is unknown. Although most of the traits/genes listed here are shown as dominant/recessive, some traits once thought to be controlled by simple Mendelian inheritance principles are actually influenced by one or more modifier genes.

Some genes are hypothetical or under debate i.e. an effect has been observed, but the existence of a single gene governing that effect has not been proven.

BASIC COLOUR GENES

There are two types of colour pigment - eumelanin (black/brown pigment) and phaeomelanin (yellow/red pigment). There are several mutant forms of the black/brown pigment. The coat colour depends on which pigments are present. A number of other genes modify the amount of pigment in the hair shaft and whether it is laid down in alternating light and dark bands along the shaft or as a single, solid band stretching from follicle to hair tip. At the foot of this page there is a more detailed description of how melanin works to give a wide array of colours.

 

Dominant

Recessive(s)

Notes

Colour/Albino

C - full colour

c - pink-eyed albino
ca - blue-eyed albino
cb- Burmese
cs - Siamese

cscb = Tonkinese

Agouti

A - agouti

a - non-agouti

Wild-type is agouti

Black/brown

B - black/brown

b - chocolate
bl - cinnamon

 

Dilution

D - dense

d - dilute

 

Orange

O

o - wild-type

Sex-linked

White

W - white

w - non-white

Masks other colours

 

Colour Modifier Genes

These are genes that modify the action of other genes giving more subtle variations on the basic colour. Although it could be argued that dense/dilute modifies the colour, it is listed as a basic colour.

 

Gene Symbol

Notes

Black Modifier (Amber or Fox)

Bm

recessive

Dilute Modifier

Dm

Dominant, but only affects cats that are homozygous for dilute "d"

Colour Inhibitor

I

Dominant gene giving silver undercoat

 

PATTERN GENES

Colourpoint is not included here as it is a form of albinism. These genes affect the distribution of colour on the body. Some of the posited genes have been given symbols by breeders, but are not widely accepted. You will find that outdated texts give Ta as ticked tabby, Tm as mackerel tabby and Tc as classic tabby and describe them as alleles of a single "tabby" gene. This was later proved incorrect. Tm and Tc are no longer used; mackerel is now Mc and classic tabby is mc. Ticked tabby is a different gene and remains Ta although some early research designated it U for "unstriped tabby".

 

Dominant

Recessive

Notes

Bengal Glitter

 

gl

 

Melanin Inhibitor

I - silver

i

Silver (ii = gold)

Ojos Azules

??

 

Dominant, causes blue eyes and white splashed extremeties

Spotted Tabby

Sp

 

Egyptian Mau type spots

Tabby Pattern

Mc- mackerel

mc - classic

 

Tabby Pattern Modifier - size

Thl - large pattern classic tabby

ths - small pattern classic tabby (Sokoke type)

Posited for Australian Mist, interacts with mackerel or classic tabby to determine blotch size/density

Tabby Pattern Modifier - spots

Pmf - modified tabby

pmu - unmodified tabby

Posited for Australian Mist, interacts with mackerel or classic tabby to give small or large spots respectively

Ticked Tabby

T a- Abyssinian ticked

ta - non Aby ticked

Originally thought to be an allele of Tabby Pattern

Unstriped Tabby

U

u

Alternative symbol for Ticked tabby

White Gloving (Birman)

G - white gloving (in Birmans breed).

N - non-white gloved

Birman white gloving is recessive.
Breeds other than Birmans may have white mitting due to other genes

White Spotting

Sb - white mitting (except Birmans).
Sp - particolour
S - piebald

s - non-spotted

S is semi-dominant; Sb and Sp are posited
Breeds other than Birmans have white mitting, but may not have the "White Gloving" gene

Wide band

Wb

 

Determines width of silver/gold undercoat band caused by inhibitor gene.

 

FUR TYPE GENES

These are fur type anomalies that are (or have been) selectively bred; some of the newer ones have not been allocated symbols. At the time of writing there are also several "new" rexes whose genetic make-up has not yet been determined.

 

Gene Symbol

Notes

Cornish Rex

r

recessive

Devon Rex

re

recessive
Sphynx & Devon Rex are different mutations of the same allele (same locus. Devon Rex is recessive to Sphynx.)

Dutch Rex

Rd

dominant

Long hair

l

recessive

Hairless (French)

h

recessive

Hairless (Hawaiian)

hr

DNA analysis found this to be same mutation as Sphynx with other effects being due to interaction/recombination of genes on other loci

Hairless (Redcar hairless)

hd

Recessive, lethal (British hairless mutation)

Hairless (Mexican)

??

?? Extinct, distinct from known mutations

Hairless (Russian)

??

dominant (occurred in Donskoy)

Hairless (Sphynx)

hr

Recessive; Canadian Sphynx breed.
Sphynx & Devon Rex are different mutations of the same allele (same locus). Sphynx is dominant to Devon Rex.

LaPerm

Lp

dominant

Oregon Rex

ro

recessive

Recessive Shorthair

??

recessive. Shorthair is normally dominant over longhair, but some Persian lines (should breed true for recessive longhair gene) have produced shorthair offspring.

Selkirk Rex

Se

dominant

Wirehair

Wh

Dominant (poss incomplete)

York Choc Undercoat

Yuc
yuc

Dominant, lacks undercoat (posited)
Recessive, full undercoat (posited)

 

BODY TYPE GENES

These are conformation anomalies that are selectively bred.

 

Gene Symbol

Notes

Bobtail (Japanese, Karelian)

Jb

Recessive

Bobtail (Kurelian)

??

Incomplete Dominant

Curled Ear

Cu

dominant

Folded Ear

Fd

Dominant, incomplete penetrance

Manx

M

dominant

Munchkin

Mk

dominant

Polydactyl

Pd

Incomplete penetrance (this is "classic polydactyly"; there may also be other mutations producing polydactyly

 

 ABNORMALITIES

This list excludes those abnormalities that have been developed as breed traits. The list includes both physical and physiological anomalies.

Abnormality

Gene Symbol

Notes

Brachyury (short tail)

br

recessive

Chediak-Higashi syndrome

ch

Recessive

Cutaneous asthenia ("winged cat syndrome")

Cut

dominant

Episodic weakness

ew

Recessive (provisional symbol)

Flat Chested

fck

Recessive (provisional symbol)

Four Ears (duplicate pinnae)

dp

Recessive

Gangliosidosis GM1

ga-1

recessive

Gangliosidosis GM2

ga-2

recessive

Haemophilia A

Hma

Sex-linked

Haemophilia B

Hmb

Sex-linked

Hageman Factor Deficiency

Hag

Dominant (incomplete)

Hydrocephaly

hy

recessive

Hyperoxaluria

ho

recessive

Hyperchylomicronemia

hce

recessive

Mannosidosis

man

recessive

Meningoencephalocele

mc

recessive

Mucopolysaccharidosis-1

mps-1

recessive

Mucopolysaccharidosis-6

mps-6

recessive

Mucopolysaccharidosis-7

mps-7

recessive

Neuroaxonal dystrophy

no

recessive

Pelger-Huet Anomaly

Ph

Dominant

Polycystic Kidney Disease

??

 

Porphyria

Po

Dominant

Progressive Retinal Atrophy

rdg

Recessive (Sweden)

Progressive Retinal Atrophy (Rod-Cone Dysplasia)

Rdy

Dominant (UK)

Retinal degeneration

rt

recessive

Sparse fur

sp

recessive

Spasticity

spt

Recessive

Spheroid lysosomal disease

si

recessive

Sphingomyelinosis

spi

Recessive

Split Foot (syndactyly)

Sh

Dominant

Testicular feminisation

tfm

Recessive

Tremor

tr

Recessive

 

HOW MELANIN PRODUCES MANY COLOURS

Colour is caused by the melanin pigment. There are two distinct types of melanin in the cat: eumelanin (black-based) and phaeomelanin (red/yellow-based). Eumelanin is, in the absence of colour modifer genes, black or dark brown (seal). Phaeomelanin is, in the absence of colour modifer genes, a yellowish/orangey colour known to cat fanciers as "red". Melanin is deposited on the hair shaft as the hair grows, but is not deposited at a constant rate. This results in the darker tips frequently seen on hairs. The Agouti protein affects the deposition of melanin in the growing hair and results in the banding effect (several bands of dark and light along the hair shaft). It causes alternating, distinct bands of eumelanin (black/brown) and phaeomelanin (red/yellow).

The mutant "Non-Agouti" form of the Agouti protein inhibits the banding effect and results in solid coloured hairs or hairs. The Tabby pattern genes inhibits the action of the Agouti gene in certain areas of the coat resulting in some agouti areas (ticked background colour) and some non-agouti areas (pattern). Sex-linked Red replaces the eumelanin in the growing hairs with phaeomelanin - the hairs are still ticked, but the bands of colour are light and dark red. Unlike eumelanin, phaeomelanin pigment is not greatly inhibited by the Non-Agouti protein hence red cats always show a tabby pattern.

Tortoiseshell cats have a patchwork effect; some areas of the coat have eumelanin while other areas have phaeomelanin. The eumelanistic areas are affected by tabby, non-agouti etc, but the phaeomelanin areas are not. As a result, the tabby pattern still shows up on the red areas regardless of whether the cat is a tortie or a tabby-tortie. A series of "rufous polygenes" affect the richness of the red colour - ranging from yellow-orange through to rich orange-red.

The B (black/brown) gene has a lightening effect on eumelanin. Depending on which of the B genes a cat has, the coat can be black/brown, chocolate or cinnamon. The D (dense/dilute) gene affects the density of pigment in the hair and affects both eumelanin and phaeomelanin. The effect is a washed out version of the original colour e.g. black becomes blue, red becomes cream. The Dm (dilute modifier) gene only affects the colour if the cats are already dilute (homozygous for the dilution gene). It "browns" or "caramelises" the diluted colour e.g. blue becomes caramel, cream becomes apricot.

 

Black/Brown Gene

Dilution

Dilute Modifier

Eumelanistic Colour

B-

D-

any

Brown/Black
(dilute modifier does not affect non-dilute colours)

B-

dd

dmdm

Blue

B-

dd

Dm-

Caramel (blue based caramel)

bb or bbl

D-

any

Chocolate

bb or bbl

dd

dmdm

Lilac

bb or bbl

dd

Dm-

Taupe (lilac based caramel)

blbl

D-

any

Cinnamon

blbl

dd

dmdm

Fawn

blbl

dd

Dm-

Fawn based Caramel

 

 

Red Gene

Dilution

Dilute Modifier

Phaeomelanistic Colour

O

D-

any

Red

O

dd

dmdm

Cream

O

dd

Dm-

Apricot

 

The C (full colour) gene comes in various flavours and causes different types of albino. Not all albinos are pure white! The C gene affects the intensity of melanin production. The normal (dominant form) is "full colour". The mutant forms affect the colour intensity and are temperature sensitive - the higher the temperature, the more effective they are. Cb is the Burmese factor and is only slightly temperature sensitive; it causes a slight lightening of black (eumelanin) to brown (sable) and of orange (phaeomelanin) to a yellow colour. Cs is the Siamese factor and is much more temperature sensitive; it has a much greater lightening effect than the Burmese factor causing greater contrast between the body colour and the points. Cats that have one copy of the Burmese factor and one copy of the Siamese factor show an intermediate effect known as Tonkinese. The most recessive form is c which is the rare pink-eyed albino totally lacking in pigment. Ca is the blue-eyed albino where there is a very small amount of pigment.

Further Reading:

Robinson's Genetics for Cat Breeders. This is currently in its 4th Edition (1999) and is the cat breeder's bible. However, further genes and a lot more mutations have been identified since it was published in 1999 and an updated version is eagerly awaited.

MESSYBEAST : BASIC GENETICS FOR BREEDERS & CAT LOVERS