Coat Colours - Geno
Agouti
A(w) - Agouti White Bellied Dominant.Effect = Rat is agouti and it's belly is white.
Veterinarian Resources; Vasenius L. Genetics of the white bellied agouti colour in the Norway rat. Z Versuchstierkd. 1972;14(3):142-7.
A- Wild Type, Agouti Dominant.
Effect = The rat has black hairs with a yellow band in them. The belly is slightly lighter than the fur on the back, somewhat "grey" overall.
a-Recessive, Non-agouti.
Effect = Rat is a "solid" colour with no yellow "bands" in the hairs. If no other colour modifiers are present, a homozygous (a/a) rat would appear black.
Brown Locus
The brown locus is often scientifically denoted as Tyrp1 with either (B) or (b) shown in superscript or in brackets after it. Most fanciers though just use B and b. This mutation's chromosomal location is 5q33B - Black Dominant.
Effect = No Dilution effect.
b- Brown Recessive.
Effect = The homozygous non-agouti chocolate ( a/a b/b ) is commonly called "chocolate" in the fancy.
Homozygous with agouti ( A/* b/b) it creates a dark cinnamon colour.
Colour Locus
The colour locus is often scientifically denoted as Tyr with the "c" symbols shown in superscript or in brackets after it. Most fanciers though just use the "c" symbols shown below. This mutations is on chromosome #1Tyrosine makes melanin from which both Eumelanin and phaeomelanin are derived. Abscence of melanin pigment results in Albinism which is a common mutation on this locus. Following are a list of mutations at this locus which are recessive. If they are not activated, the the rat will display the full colour of what ever other coat colour modifiers are present.
C - Colour Dominant.
Effect = Rat appears the colour/marking which is determined by other locus.
c(h)- Himalayan
Effect = When homozygotes, the babies are a uniform light tan; after their first molt, most of the coat lightens but the ears, nose, tail, and scrotum become dark as in Siamese cats and is refered to in the fancy as a "siamese".
When combined with albanism (c(h)/c), the result is half way between albino and siamese and in the fancy is called a "himalayan".
Veterinarian Resources; Moutier R, et al. Himalayan allele at the albino locus in them Norway rat. Journal of Heredity. 1973 Sep; 64(5): 303-304
Fitzgerald, Roxanne . Siamese Rat Genetics. Rat & Mouse Gazette. May/June 1997.
c(d) - Ruby Dilution Recessive.
Effect = Agouti'd Homozygotes are devoid of yellow pigment. The black hair tips are a light sepia and the middle and base of the hairs are faded to white.
On non agouti homozygotes, the rat has sepia hairs with white hair bases.
Heterozygotes split with agouti are intermediate between albino and ruby-eye dilute homozygotes. This mutation may be extinct.
Veterinarian Resources; Robinson, Roy. Genetics of the Norway Rat. Pergamon Press 1965. pages 15-16. (discusses C, C(d) and c)
c - Albino Recessive.
Effect = Homozygotes are white furred and light pink eyed. They have extreemly poor eyesight due to lack of retinal pigment.
Density Locus
The Density locus has previously been scientifically denoted as Myh12 and D and Dop. It is now labled as Myo5a with the "d" symbols shown in superscript or in brackets after it. Most fanciers though just use the "d" symbols shown below. This mutations is on chromosome #8.This mutation appears to be homologous to the similar mutation in the mouse that creates the "d" related "blue" seen in the fancy. The similarity is in terms of clinical symptoms, coat colour effect and chromosomal location of the gene loci.
D - Wild Type Dominant.
Effect = No alteration of colour/pigment.
d- Density / Dilute Recessive.
Effect = Causing light coat colour. In nonagouti form the coat colour is a a very dark slate blue colour and black eyes, commonly called "Russian Blue".
Veterinarian Resources; Debbie Ducommun, Fancy Rats: New Colors, Coat Patterns and Mutations Fuel the Growing Interest in Pet Rats. Critters USA, 1998
Tamr†ttans V„nner. Blue rats and genetics
Robinson, Roy. Genetics of the Norway Rat Pergamon Press, 1965. Pg 18
d(l) - Density / dilute Lethal Recessive.
Effect = Causing ataxia and coat color dilution. Affected rats develop severe neuromuscular disorders including convulsions and opisthotonus (arching upward of the head and tail). Death usually comes around the age of weening or slightly after.
Veterinarian Resources; Ohno, K. Mapping of the dilute-opisthotonus (dop) gene on chromosome 8 of the rat. Journal: Experimental Animal. Volume: 45 Pages: 71-75 Year: 1996
Dekker-Ohno K, et al. An ataxic mutant rat with dilute coat color. Lab Anim Sci. 1993 Aug; 43(4): 370-372.
Mink Locus
This mutation is found on Chromosome #3 M - Wild Type Dominant.Effect = No Dilution effect.
m- Mink Recessive.
Effect = Homozygous on a non-agouti background (a/a m/m) the effect is a brown coat which in good colour bred lines is a dark milk chocolate with black eyes, but when randomly bred, other colour modifiers can interact with it to make it warmer with lighter eyes (ruby eyed mocha) or paler (lilac). It has variable white undercoat ( varies from barely detectable to obvious white). Mink interacts with agouti (A/*m/m) similarily to how brown interacts with agouti- creating the "cinnamon" phenotype, but with more orange (which has become the preferred show cinnamon animal in many clubs).
Veterinarian Resources; The colour safir. by Ann-Zophi P†lsson.
Robinson, Roy. Mink and Pearl: New color mutants in the Norway rat. The Journal of Heredity Volume: 85 Pages: 142-143 Year: 1994
Pink Eye Locus
This locus may also be seen in scientific literature as symbolized "Oca2" or called "Oculocutaneous albinism II". Most fanciers just use the symbol "p" however. It is located on Chromosome #1. P - Wild Type Dominant.Effect = No Dilution effect.
p- Pink Eye Dilution Recessive.
Effect = Dilutes non-agouti rats to a "champagne" colour (a/a p/p) and agouti ones to the USA standardized colour "amber" (A/* p/p).
Veterinarian Resources; LaVail MM. Fawn-hooded rats, the fawn mutation and interaction of pink-eyed and red-eyed dilution genes. Journal of Heredity 1981 Jul;72(4):286-287
Tamr†ttans V„nner orange rats and genetics.
Pearl Locus
Pearl is on Chromosome #3, closely linked to Agouti with a .73 +/- .42 recombinantion dominant lethal mutation. Pearl produces both a white and one that is pale cream with variable dark brown tips to the hairs. It is lethal in homozygous form. It displays if mink is homozygous but is hypostatic to other color genes (IOW: it can not display over non-mink colours). Pe - Pearl Dominant.Effect = Pearl adds a significant amount of white (or in cases, "off-white" to the rat's coat, leaving a small "tip" of colours on some hairs and leaving a few full or mostly coloured hairs through out the coat. If agoutis is present also (A/* Pe/- m/m) then the rat will be a cinnamon-pearl. It is lethal in homozygous form, hense, Pe/Pe rats are never born. It also displays ONLY if mink is homozygous. So a Pe/- m/m rat will appear pearl but a Pe/- M/m or Pe/- M/M rat, while geneticlally pearl, will not appear pearled.
Veterinarian Resources; Robinson, Roy. Mink and Pearl: New color mutants in the Norway rat. The Journal of Heredity Volume: 85 Pages: 142-143 Year: 1994.
Johansson, Eva and Ann-Zophi P†lsson. The Colour Cinnamon Pearl
pe- Wild Type Recessive.
Effect = None.
Red Eye Locus
Located on Chromosome #1. Often called "Ruby eyed Dilution" by some fanciers, but the term "ruby" should be reserved for a mutation (yet to be identified in rats) that is seen in other animals, such as mice, that creates a dark grey coat colour with ruby eyes. R - Wild Type Dominant.Effect = No Dilution effect.
r- Red Eye Dilution Recessive.
Effect = Dilutes non-agouti rats (a/a r/r) are "beige" and dilutes agouti based rats (A/* r/r) are "fawn". Eyes are medium to dark ruby.
Veterinarian Resources; LaVail MM. Fawn-hooded rats, the fawn mutation and interaction of pink-eyed and red-eyed dilution genes. Journal of Heredity 1981 Jul;72(4):286-287
Tamr†ttans V„nner orange rats and genetics.
Prieur DJ, Meyers KM. Genetics of the fawn-hooded rat strain. Journal of Heredity 1984 Sep;75(5):349-352
Sand Locus
This mutation was first found in wild rattus norvegicus animals, in Oaklahoma. The mutation was believed to go extinct, but is found re-mention of it in the book listed below, however, no description. Sd - Wild Type Dominant.Effect = No Dilution effect.
sd- Sand Dilution Recessive mutaiton.
Effect = Combined with agouti (A/*sd/sd) the rat is a brown-yellow. On a non-agotui backgrounds, (a/a sd/sd) the rat appears "dark grey" or "off black" (darker than our blues but with no "coolness" to it). It can apparently be combined with chocolates to create a very "red" coloured rat.
Veterinarian Resources; Schwartz, Daniel R. Dr., Rats: A Complete introduction TFH publishing, YearBooks Inc. ISB: 0-7938-0204-0 pg 11.
Sinclair, Linda. Rat Resume The Rat and Mouse gazette, RMCA, Vol 3 is.1 Pg. 14
Smoke Locus
This mutation is on Chromosome: #5. It was originally labelled "Silvering" by Castle, but the description of was more of a smoking effect rather than of silvering. Later, Roy Robinson, in the book "Genetics of the Norway Rat", discussed actual silvered rats that had been discovered and interested the rat fancy for breeding and compaired these to Castle's original "Silvered" (smoked) rats and suggested that a new name be found for Castle's mutation. Sm - Wild Type Dominant.Effect = None.
sm- Smoking Recessive Mutation.
Effect = Causing the base of hairs to be white or cream, resulting in an appearance similar to that of "smoke" in cats.
Veterinarian Resources; W. E. Castle Silver, a new mutation of the rat. Journal of Heredity Volume: 44Pages: 205-206Year: 1953
Silvering Locus
Si - Wild Type Dominant.Effect = None.
si- Silvering A Recessive Mutation.
Effect = Causing white hairs to be dispersed throughout the fur all over the body.
Grey Locus
Not yet scientifically described.G - Wild Type Dominant.
Effect = No Dilution effect.
g- Grey (aka: blue) Recessive.
Effect = Rats that are a/a g/g appear a medium slate grey colour.
Rescources; Tamrýttans V,nner. Blue rats and genetics.
Fawn Locus
Supposedly, the colour "Fawn" resembles our "modern" mink (m), but without the white hair bases. Roy Robinson considered mink as a possible re-mutation or allele (indeed they were both mapped to chromosome #3) but could not locate a known source of fawn (f), in order to verify the possibility. Other cases of examining fawns as well have turned up no more "fawn"(f) type rats in the scientific world. However, it may exist remotely, in breeder or feeder stock, being mistaken for other colours such as mink or coffee.F - Wild Type Dominant.
Effect = No Dilution effect.
f- Fawn Recessive.
Effect Rats that are a/a f/f are a "coffee" like colour and those that are a/a d/d f/f are descried as being "lavander". Experimenters working with the colour were unable to obtain agouti'd fawn rats despite breeding for it.
Extention Locus
The extension locus is very common in mammals. It exists in fancy mice. In mice, alleles at this locus interact with those at the agouti locus. Dominant extension alleles make an animal's coat appear more black where as recessive alleles increase the yellow colour we see.Its not confirmed if this locus is known in rats yet. The only scientific or fancy literature on the subject, is a book by Dr. Daniel R Swartz, "Rats: A Complete Introduction" (TFH publications and yearbooks inc, ISBN: 0-7938-0204-0). In this book, "Yellow (e/e)" is listed as a coat colour variety but there is unfortunatly no description or photo of the rat. It has only entred simply because occassionally there is murmurrings of such a colour, yet it apparently is quite ellusive! Whether it exists is not certain, though because of the commonest of an extention locus in mammals, its likely that it either does or will soon be discovered. As with mice, the appearance would probably be with a E/- (dominant black) an all black rat and with e/e (recessive yellow) a very clear, bright yellow or light orange colour with no ticking pattern and black eyes.
These are only THEORETICAL and may NOT YET EXIST! E - Black Dominant. Possible Effect = Makes a rat black reguardless of most other dilutions or presence of agouti trait.
e- Extention of Yellow Recessive.
Possible Effect = The homozygous yellow (e/e) rat would appear a bright and clear yellow colour, similar to that of the fancy gold mouse. The eyes would be black.
e(p)- Partial Extention.
Possible Effect = This recessive mutation is known to exist in other species to create red-black patched animals and when combined with white spotting, tri-coloured animals. Its unlikely the fancy ever had a tricoloured rat, and we shouldn't hold our breath for one to appear. But if by chance one DOES appear, this is a likely locus to consider for the location of that mutation.
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