Cat World > Interesting Stuff > Feline Genetic Loci Table

Feline Genetic Loci Table

Coat Colour 

B - Brown Locus 

Genotype Description Phenotype 
B/B Homozygous - Black/Brown  Black/Brown
B/b Heterozygous - Black/Brown - carries Chocolate Black
B/bl Heterozygous - Black/Brown - carries Cinnamon Black
b/b Homozygous - Chocolate Chocolate
bl/bl Homozygous - Cinnamon Cinnamon - reddish chocolate
b/bl Heterozygous - Chocolate - carries Cinnamon Chocolate 
The Chocolate allele whilst recessive to the Black allele is dominant to cinnamon. Thus a chocolate cat can carry the cinnamon allele, a Black cat can carry either chocolate or cinnamon and a cinnamon cat can only be homozygous cinnamon.
ba - Barrington Brown Locus (example only)
Genotype Description Phenotype 
Ba/Ba Homozygous - Non Barrington Brown Cat unaffected - ie Black/Brown/Chocolate etc
Ba/ba Heterozygous - Non Barrington Brown - carries Barrington Brown Cat unaffected - ie Black/Brown/Chocolate etc
ba/ba Homozygous - Barrington Brown -liberty of renaming  Mahogany Brown/Light Brown/milk coffee in colour
I took the liberty of renaming Shaw's Barrington Brown allele so that it could be used as an example of a recessive brown locus in this table. The Barrington brown cats were b/b/, ba/ba - the two alleles had an additive effect on each other and created the pale milk coffee coloured cats. It has only been added as an example as they colony of cats were never seen outside the laboratory nor did any of the cats leave the laboratory. But it is an example of a further recessive brown locus.

O - Red Locus

Geneotype Description Phenotype
XO/XO  Homozygous - Red Female Red Series female
XO/Xo Heterozygous - Tortishell female Female Red Series intermingled with other base colour i.e.. Black tortie, chocolate tortie
Xo/Xo Homozygous - Non-red female no effect - no red or tortoiseshell
XO/Y Red Male Red Series male
XoY Non-red male No effect - no red
XXY & similar Mosaic  Red series intermingled with base colour - i.e.. Black tortie (unusual)

Sex linked to the X chromosome. Cream is the dilution of red and thus also sex linked and Apricot is the Dilute modifier variations of cream and thus also sex linked. E.g.. d/d, dm/dm, XO/XO = cream; d/d, Dm/-, XO/XO = Apricot 

C - Colouration Locus 
Genotype Description Phenotype
C/C Homozygous - Solid Coloured Cat solid colour
C/c Heterozygous - Solid Coloured carrying red eyed albino Cat solid colour
C/ca Heterozygous -Solid Coloured carrying blue eyed albino Cat solid colour
C/cs Heterozygous - Solid Coloured carrying colour point Cat solid colour
C/cb Heterozygous - Solid Coloured carrying sepia Cat solid colour
c/c Homozygous - Pink eyed Albino (recessive white)  No Pigment (Albino) White cat with Pink eyes
ca/ca Homozygous - Blue eyed Albino (recessive white) No Pigment (Albino) White cat with pale blue eyes
cs/cs Homozygous - Colour Point Pointing/Siamese - high grade point definition
cb/cb Homozygous- Sepia  Sepia/Burmese- low grade point definition
cb/cs Heterozygous- Mink - Sepia & Point (co-dominant) Mink/Tonkinese - mid range point definition
cs/ca Heterozygous - Bondanese  Pointing/Siamese - high grade point definition, with paler coat 
cb/ca * - heterozygous- Sepia & Blue eyed albino Not enough information to determine phenotype
cs/c * - heterozygous Point & Red eyed albino Not enough information to determine phenotype
cb/c * - heterozygous Sepia & Red eyed albino Not enough information to determine phenotype
ca/c * - heterozygous Blue eyed albino & Red eyed Albino No Pigment (Albino) White cat with pale blue eyes
*The combinations above have been given no names. The gametes cb and cs are co-dominant to each other and create mid range point definition known as a mink cb/cs. There is little data on the gametes ca, c and their effects on cb and cs.
D - Colour Density Locus 
Genotype Description Phenotype
D/D Homozygous - Dense - Darker pigmentation  Cat dark colour, e.g., black, chocolate, cinnamon, red etc.
D/d Heterozygous - Dense - carrier of dilution Cat dark colour, e.g., black, chocolate, cinnamon, red etc.
d/d Heterozygous - Dilute Dilutes colours - e.g. blue: B/-,DD, lilac: b/b, d/d, cinnamon: bl/bl,d/d
Dense and Dilute colours: Black (B/-,D-) = Blue (B/-,d/d); Chocolate (b/b, D/-) = Lilac (b/b, d/d); Cinnamon (bl/bl, D/-) = Fawn (bl/bl, d/d); Red (XO/XO, D/-) = cream (XO/XO, d/d)at
Dm - Dilute Modifier Locus
Genotype Description Phenotype
Dm/Dm Homozygous - Dilute Modifier  Modifies Dilutes - caramel tone 
Dm/dm Heterozygous - Dilute Modifier - carrier of non dilute modifier Modifies Dilutes - caramel tone 
dm/dm Homozygous - Non-dilute Modifier  No effect
The Dilute Modifier only effects dilute colours. It has no effect on Dense colours. Thus for the phenotype to be effected by the Dilute modifier the cat needs the genotype (d/d, Dm/-). A cat that is (D/d, Dm/-) may possess the Dilute modifier allele but the coat is unaffected because the Dm allele only effects dilutes.
S - White Piebald Spotting Locus 
Genotype Description Phenotype
SS Homozygous - White Piebald spotted Medium to high levels of white spotting
S/s Heterozygous - White spotted carries non-spotting Low to medium levels of white spotting
s/s Homozygous - Non White Piebald-spotting. No white spotting, solid coloured cat.
The Piebald allele displays variable expression - control of this expression is as yet undetermined. However generally cats with high grade white markings, such as harlequin and Vans, tend to be homozygous Piebald.
W - White Locus 
Genotype Description Phenotype
W/W Homozygous - White All white coat masking cats colour
W/w Heterozygous - White - carrying non white All white coat masking cats colour
w/w Homozygous - Non white No effect - no white
The white allele can also cause a developmental cascade of events where open the melanocytes fail to migrate over they eyes (resulting in blue eyes or one blue eye) and/or cause degenerative changes to occur in the succule and cochlea caused by lack of migration or viable migration (resulting in partial or total hearing loss).
Agouti Variations & Inhibitors- Tabby patterns & Smoke/Silvers
A - Agouti Locus 
Genotype Description Phenotype 
A/A Homozygous - Agouti  Agouti banding of the hair shaft
A/a Heterozygous - Agouti - carries non-agouti Agouti banding of the hair shaft
a/a Homozygous - Non-Agouti No banding of the hair shaft
This allele determines the phenotypic absence or presence of the Tabby alleles. The variation in Agouti banding is determined by the Tabby Allele Series - see below
Mc/mc - Mackerel Tabby/Classic Tabby Locus
Genotype Description Phenotype
Mc/Mc Homozygous - Mackerel Tabby  Mackerel Tabby
Mc/mc Heterozygous- Mackerel - carrying Classic Tabby Mackerel Tabby
mc/mc Homozygous - Classic Tabby Classic Tabby Markings on coat
Both Mackerel and Classic tabbies are modified by ticked tabby allele and the spotted tabby allele. They must have non ticked (ta/ta) and non spotted (sp/sp) alleles present in order to allow the Mackerel/Classic tabby allele to display its phenotype, e.g.: ta/ta sp/sp, Mc/mc = mackerel tabby carrying classic tabby allele (with no ticking or spotting). See Ticked tabby Locus for another eg.
Sp - Spotted Tabby Locus 
Genotype Description Phenotype
Sp/Sp Homozygous - Spotted Tabby Spotted Tabby
Sp/sp Heterozygous - Spotted Tabby - carrying non spotted Spotted Tabby
sp/sp Homozygous - Non Spotted Tabby  No effect
The Spotted Tabby allele is a dominate modifier of both the mackerel and classic tabby allele, but is recessive to the ticked tabby modifier allele. e.g. ta/ta, SP/sp, Mc/mc = Spotted tabby carrying non spotting allele, masking the mackerel tabby allele carrying the classic tabby allele (with no ticking)
Ta - Ticked Tabby Locus 
Geneotype Description Phenotype
Ta/Ta Homozygous - Ticked Tabby Ticked Tabby
Ta/ta Heterozygous - Ticked Tabby Ticked Tabby
ta/ta Homozygous - Non Ticked Tabby No Effect
Ticked tabby allele is a dominant modifier to all other Agouti variations. The cat must have ta/ta to see the other variations. E.g., TA/ta, SP/sp, Mc/mc = is a ticked tabby carrying non ticked tabby and masking Spotting, carrying non spotting and masking the Mackerel tabby allele that carries the classic tabby allele. See above for more examples.
I - Inhibitor Locus 
Geneotype Description Phenotype
I/I Homozygous - Inhibitor - Silver Smoke/silver tabby/tipped/shaded - base to mid - to upper hair shaft white
I/i Heterozygous - Inhibitor - carrier of non-inhibitor Smoke/silver tabby/tipped/shaded - base to mid - to upper hair shaft white
i/i Homozygous - Non Inhibitor  No effect
The inhibitor allele has variable expressions in combination with the agouti and non-agouti alleles and variable banding on the hair shaft. Smokes are the non-agouti inhibitor combination and of course the silver tabbies are the agouti-inhibitor combination. Chinchilla/shaded/tipped are also inhibitor agouti combination but with the addition of wide banding on the hair shaft. The Inhibitor allele can combine with all agouti variations (Silver tabby series)
Coat texture/Length
L - Hair Length Locus
Genotype Description Phenotype
L/L Homozygous - Shorthair Shorthair
L/l Heterozygous - Shorthair - carries long hair Shorthair
l/l Homozygous - longhair  Longhair
The longhair allele displays variations in length- for semi longhair of the Turkish Angora, to the longhair of the Persian (phenotypically different coats but the alleles that control the hair length are the same). The shorthair allele also is variable, from the short coat of the Siamese to the short coat of the Exotic shorthair (phenotypicaly different coats but the alleles that control them are the same)
ls - Recessive Shorthair (no gene code has been allocated - this is only being used as an examples)
Genotype Description Phenotype
Ls/Ls Homozygous - Longhair Longhair 
Ls/ls Heterozygous - Longhair - carries short hair Longhair
ls/ls Homozygous - Shorthair Shorthair
This is a (rare) autosomal recessive shorthair to Longhair. And has been found in some Persians lines. Shorthaired kittens are produced from longhaired cats. 
r - Cornish Rexing Locus 
Genotype Description Phenotype
R/R Homozygous - Straight haired cat Standard coat - no effect
R/r Heterozygous - Straight haired cat carries - C rexing Standard coat - no effect
r/r Homozygous - C rexed cat Rexed - wavy fur
The curly coat resulting from the Cornish rex allele is recessive to normal coats but is co-dominate to the Devon Rexing allele. A cross between a Devon and a Cornish Rex results in a straight coated cat because they are on two different Loci. First cross would get R/r Re/r. But a further cross between offspring could result in 1/16 r/r re/re - a cat that is both a Cornish rex and a Devon rexoat
re - Devon Rexing Locus 
Genotype Description Phenotype
Re/Re Homozygous - Straight haired cat Standard coat - no effect
Re/re Heterozygous - Straight haired cat carries - D rexing Standard coat - no effect
re/re Homozygous - D rexed cat Rexed - wavy fur
The curly coat resulting from the Devon Rex allele is recessive to normal coats but is co-dominate to the Cornish Rexing allele. See above.. The Devon Rex allele is however recessive to the Sphynx allele.
ro - Oragon Rexing Locus 
Genotype Description Phenotype
Ro/Ro Homozygous - Straight haired cat Standard coat - no effect
Ro/ro Heterozygous - Straight haired cat carries - O rexing Standard coat - no effect
ro/ro Homozygous - O rexed cat Rexed - wavy fur
The curly coat resulting from the Oragon Rex allele is recessive to normal coat and on a different locus to both the Cornish and Devon rexing allele a cross between the Oragon Rex and either the Cornish or Devon rex results in a cat with a straight coat. This cat is no longer bred.
Se - Selkirk Rexing curl Locus 
Genotype Description Phenotype
Se/Se Homozygous - S Rex cat Rexed - wavy fur
Se/se Heterozygous - S Rexed cat - carrying normal coat Rexed - wavy fur
se/se Homozygous - Straight haired cat Standard coat - no effect
The curly coat resulting from the Selkirk allele is a dominant trait and thus can carry straight The homozygous Selkirk has a finer, curlier and sparser coat than the heterozygous Selkirk. Thus all show Selkirks are heterozygous.
Lp - Laperm Rexing Locos - (I can find no gene code allocated - this is only being used as an examples)
Genotype Description Phenotype
LP/LP Homozygous - LP Rex cat Rexed - wavy fur
LP/lp Heterozygous - LP Rexed cat - carrying normal coat Rexed - wavy fur
lp/lp Homozygous - Straight haired cat  Standard coat - no effect
I was unable to find the gene code (so I took liberties in using Lp - if I find the correct code this will be adjusted) But the mode of inheritance will not change and it is a good example of dominant rexing. Their coat can be wavy or have lots of ringlets
wh - Wire Hair Locus 
Genotype Description Phenotype
Wh/Wh Homozygous - Wire hair Bristly, wiry fur 
Wh/wh Heterozygous - Wire hair carries - staight hair Bristly, wiry fur 
wh/wh Homozygous - Straight hair  Standard coat - no effect
The wiry coat resulting from the Wire hair allele is a dominant trait and thus the cat can carry normal hair. The Wire Hair allele has incomplete penetrance - thus cats with the dominant allele may have a normal coat - but produce cats with the wiry coat.
hr - Hairless Locus - Canadian Hairless - Sphynx cat
Genotype Description Phenotype
Hr/Hr Homozygous - Coated cat Standard coat
Hr/hr Heterozygous - Coated cat - carries Sphynx hairless allele Standard coat 
hr/hr Homozygous - Sphynx Hairless cat hairless cat 
The Sphynx allele is a receive allele and only homozygous Sphynx can be hairless. It can be carried by normal coated cats from out cross programs. They Sphynx allele is dominant to the Devon Rex allele. The French Hairless (h/h) and the UK Hairless (hd/HD - extinct) are also recessive hairless alleles - whether they are different or the same allele is uncertain and will never be known as both the UK and French Hairless are extinct..
Hp- Peterbald/Don-Sphynx Locus - (I can find no gene code allocated - this is only being used as an examples)
Genotype Description Phenotype
Hp/Hp Homozygous - Hairless Peterbald/Don-Sphynx  Hairless cat 
Hp/hp Heterozygous - Hairless -carrying normal coat Hairless cat 
hp/hp Homozygous - Coated cat Standard coat - no effect
I was unable to find the gene code (so I took liberties in using Hp - if I find the correct code this will be adjusted) But the mode of inheritance will not change and it is a good example of dominant trait. Baldness first appears on the head and neck and sometimes cats have a rex coat up to 1-2 years of age. .
Ears/Tails/Toes
Cu - Curled Ears Locus 
Genotype Description Phenotype
Cu/Cu Homozygous - Curled ears  Ears Curl backwards
Cu/cu Heterozygous - Curled Ears - carries normal ears Ears Curl backwards
cu/cu Homozygous - Normal ears Standard ears - no effect
The curled ear allele is a dominant trait that shows some variability in the degree at which the ears are curled backwards. The curled ears cats appear to have normal ears for the first 12-16 weeks and then they begin to curl backwards. Cats that are heterozygous can produce normal eared cat
Fd - Folded Ears Locus
Genotype Description Phenotype
Fd/Fd Homozygous - Folded Ears  Ears Folded Forwards 
Fd/fd Heterozygous - Folded Ears - carrying non-folded ears or standard ears (rare) Ears Folded Forwards
fd/fd Homozygous - Normal ears Standard Ears - no effect
The Folded ear allele is a dominant trait with incomplete penetrance. Homozygous folds may have cartilage defects that is rarely seen in the non folds. Thus breeders breed heterozygous folds to non folds. Unfortunately as the allele has incomplete penetrance an occasional normal eared cat from the breeding program may in fact be a heterozygous fold. Which can produce breeding problems when the normal eared off spring are used.
M - Manx tail Locus 
Genotype Description Phenotype
M/M Homozygous - Tailless Rumpy or stump - Homozygous Lethal?
M/m Heterozygous - Tailless - carrying normal tail Rumpy or stump tail
m/m Homozygous - Normal tail Standard tail - no effect
The Manx allele is a dominant trait with variable expression from complete lack of tail (Rumpy) to a foreshortened tail (stumpy). The allele has been referred to as a prenatal homozygous lethal (meaning M/M cats die in the womb) - but this is being questioned by Manx breeders. The Manx allele has been associated with several spinal cord anomalies.
Pd - Polydactyl Locus 
Genotype Description Phenotype
Pd/Pd Homozygous - Polydactyl Extra toes 
Pd/pd Heterozygous - Polydactyl - carrying normal N# toes Extra toes 
pd/pd Homozygous - Normal number of toes Standard number of toes - no effect
The main polydactyl cat trait seen is dominant in action with variable expression - effects ranging from enlargement of the inside digit, to extra toes on each foot or only the front feet. There may be other Polydactyls that appear in different gene populations that are inherited differently. 
JP Japanese Bob Tail Locus
Genotype Description Phenotype
JP/JP Homozygous - Bobtail Short bobtail 
JP/jp Heterozygous - Bobtail tail carrying normal tail Short tail 
jp/jp Homozygous- Non Japanese Bobtail Normal tail
The Japanese bobtail is thought to be a dominant trait with incomplete penetrance. Heterozygotes can have the short tail but fail to get the tail folding. This trait is thought to only occur in the homozygous bobtail
Ad - Achondroplastic Dwarfism (I can find no gene code allocated - this is only being used as an examples)
Genotype Description Phenotype
Ad/Ad Homozygous - Dwarf  Dwarf - i.e. Munchkin
Ad/ad Heterozygous - Dwarf Dwarf - i.e. Munchkin
ad/ad Homozygous - Normal sized cat Cat normal size - no effect
The dwarfism is thought to be cause be an autosomnal dominant trait. But there are questions as it may be a heterozygous lethal.
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Written by Tonia Marsh.