Rabbit Color Genetics
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The hundreds of coat colors and patterns in the domestic rabbit can be largely characterized by different combinations of alleles from only seven to ten genes. These genes act as instructions for the chemical process of melanogenesis, where pigments are produced in special cells called melanocytes and are excreted in the skin and hair follicles. Genes are inherited from the parents and come in pairs – one from the mother and one from the father. When genes mutate, their DNA sequence is slightly different and therefore the “instructions” that they contain are slightly different. Different versions of the same gene are called alleles. A non-mutated gene is known as “wild type”. For example, an American Cottontail or European Wild Rabbit has the “wild type” genes for producing their chestnut agouti color.
When a rabbit inherits one allele from its father and one from its mother, sometimes they are the same and sometimes they are different. When both alleles contain identical instructions, this is known as “homozygous” (“homo” means the same). When they are different, this is known as “heterozygous” (“hetero” means different). The instructions that an allele contains are not always expressed (visible in the coat) and this depends on how dominant the allele is. A completely dominant allele is always expressed whether it is homozygous or heterozygous. A recessive allele can only be expressed if both alleles in the gene pair are the same (homozygous) or if paired with a more-recessive allele. If a dominant and a recessive allele are paired, the recessive allele will simply be “carried” and the more-dominant allele in the pair will be expressed. To get slightly more complicated, co-dominance is another variation where two different alleles will both express at the same time. Lastly, incomplete dominant alleles will both express separately and neither is dominant. This may sound confusing now, but examples of how these actually look are further in the article. When writing out an animal’s genotype, we notate dominant alleles with upper case letters and recessive alleles with lower case letters. When there are more than two alleles possible on a single gene, the context of an allele being dominant or recessive may change depending on what allele it is being compared to. If an allele is unknown, we use a “-“ in the genotype.
Most color patterns in rabbits can be broken down into 7 main genes also known as loci which is the specific location on the chromosome. These are notated as A, B, C, D, E, En, and V. There are many other genes relating to coat color besides these main 7, and I have additionally described the W, Du, Si, and P genes which are a little less common or more-breed-specific. Many other variations that we see are due to complex modifier genes which are difficult to characterize, but function by modifying the expression of a different gene and are often additive in nature.
A wild-type rabbit has the genotype of AABBCCDDEEenenVVWWD(u)D(u)s(i)s(i)PP. Visually, this is chestnut agouti coloration. Wild rabbits will usually have this genotype. Domestic rabbits can also be wild-type in their main color genetics. All other colors are a result of mutations to one or more of these wild-type genes. Don’t let the long string of letters intimidate you. Let’s now look at each gene pair and learn what each letter codes for.
Quick reference of terms used frequently in this material:
Homozygous - having two identical alleles of a particular gene
Heterozygous - having two different alleles of a particular gene
Eumelanin - black or brown types of melanin pigment, the difference being black or brown alleles on the B gene
Pheomelanin - red/yellow type of melanin pigment, the difference being intensity of modifier genes known as rufus modifiers
The color names used here are predominantly US terms. Check out the color ID page for a more detailed breakdown of common colors and alternative terminology.
B “Base color” Gene
On the base color gene, there are two alleles which code for production of two different types of eumelanin pigment. The wild type allele “B” is completely dominant and produces black eumelanin pigment and the other allele “b” is fully recessive and produces brown eumelanin pigment. Thus, you can say that all rabbits are either black or brown and every other color is simply a “pattern” where expression of either of these two pigments is modified in some way. Since black is fully dominant, a homozygous “BB” or heterozygous “Bb” animal will be indistinguishable visually and look black. Homozygous brown alleles “bb” will be brown, known as chocolate.
The brown allele also uniquely affects eye color, causing reflective red ruby cast in the pupils of homozygous animals. I believe this to be caused by a reduction in pigment expressed in the epithelium of the eye, resulting in less light being absorbed by the pupil and therefore reflecting back. The only other allele that causes a similar effect is chinchilla light on the C gene, which will be covered below.
Black – B (wild-type)
Brown - b (chocolate)
Homozygous brown alleles in place of wild-type black result in: black versus chocolate, chestnut versus chocolate agouti, blue versus lilac, tort-black versus tort-chocolate, sable point versus chocolate point, etc.
Further reading: Utzeri et al. 2014
B - Black
Black with dilution (blue)
Black with agouti banding (chestnut)
Black with chinchilla light and non-extension (sable point)
b - Brown (chocolate)
Brown with dilution (lilac)
Brown with agouti banding (chocolate agouti)
Brown with chinchilla light and non-extension (chocolate point)
Note how the eumelanin pigment in the rabbits above is distinctly black tone or brown tone regardless of the effect of other genes.
D “Dilution” Gene
The dilution gene modifies how pigment is distributed in the hair shaft. The wild type allele “D” is completely dominant with no effect to the pigment distribution and the dilute allele “d” is completely recessive and causes the pigment granules to be unevenly clumped in the hair shaft. Below is a picture I took under a microscope of hairs from a black and a blue rabbit. You can see how the pigment is clumped leaving spaces without pigment along the hair shaft in the hair from the blue. This decreases the amount of light that can be absorbed and causes the dilute appearance. The dilution also occurs in the pigment in the eyes with dense rabbits having brown eyes and dilute rabbits having blue-gray eyes with some exceptions which will be discussed later.
Dense – D (wild-type)
Dilute - d
Homozygous dilute alleles in place of wild-type dense result in: black versus blue, chestnut versus opal, chocolate versus lilac, tort-black versus tort-blue, sable point versus smoke pearl point, etc.
Further reading: Fontanesi et al. 2013
D - Dense
Dense (sable point)
d - Dilute
Dilute black (blue)
Dilute chocolate (lilac)
Dilute tort-black (tort-blue)
Dilute sable point (smoke pearl point)
Note how the pigment in the rabbits above is distinctly diluted regardless of the effect of other genes.
A “Agouti” Gene
The agouti gene controls whether or not wild type banding of eumelanin and pheomelanin pigment will occur. Remember that eumelanin is black or brown pigment. Pheomelanin pigment is red/yellow with the difference between red or yellow being controlled by modifier genes known as rufus modifiers.
Agouti – A (wild-type)
Tan Pattern – a(t)
Self - a
Further reading: Fontanesi et al. 2010, Letko et al. 2019
A - Agouti
In wild-type coloration, eumelanin and pheomelanin pigment are both produced in bands of color along the hair shaft. During the various stages of hair growth, production of eumelanin is switched on or off with pheomelanin pigment seen on the hair when the eumelanin "switch" is off. This produces the distinct bands (or "rings" of color along a single hair shaft in agouti colors. Some other alleles can turn the pheomelanin switch off which leaves nothing produced (white) if the eumelanin switch is also off (such as in chinchillas which I will discuss further). Agouti works a little differently in dorsal versus ventral parts of the body (belly, under the tail, along the inside of the ears, around the eyes, and inside the chin and legs) with decreased total pigment expression (white/light) with sharp boundaries. This distinctly lighter color on the underside and darker color on the top of the body is seen in the color of many wild animals and is thought to help camouflage them to the ground or sky depending on which direction a predator is viewing them from. In rabbits, this distinct ventral marking pattern is called "tan-pattern markings" which are seen in agoutis (plus ring color on the body) and tan-pattern (without ring color on the body) (below).
Wild-type agouti versus self or tan pattern varieties include: chestnut is the agouti version of black or black otter, chocolate agouti is the agouti version of chocolate or chocolate otter, sable chinchilla is the agouti version of siamese sable or sable marten, orange is the agouti version of tort or tort otter, etc.
Agouti banding switching between expression of eumelanin and pheomelanin. This rabbit is showing five distinct bands: eumelanin at the base of the hair, then pheomelanin, then eumelanin again, then pheomelanin, and finally eumelanin at the tips.
Agouti black (chestnut)
Agouti black and dilute (opal)
Picture credit Sunny Slope Rabbitry
Agouti black and chinchilla (bands still occur, but pheomelanin expression is also switched off, leaving white in place of red/yellow)
Picture credit Sunny Slope Rabbitry
a(t) - Tan pattern
The tan pattern allele is in between dominance of wild-type agouti and the most recessive allele, self. The visual appearance is in between, with tan pattern rabbits have the same light ventral markings that agoutis do (light belly, under the tail, along the inside of the ears, around the eyes, and inside the chin and legs), but they do not have the banding of eumelanin and pheomelanin on the rest of the body. Instead, only eumelanin is produced on the main part of the body (unless a different gene modifies that).
Tan pattern versus agouti or self varieties include: black otter is is the tan-pattern version of black or chestnut, chocolate otter is the tan-pattern version of chocolate or chocolate agouti, sable marten is the tan-pattern version of siamese sable or sable agouti, tort otter (fox) is the tan-pattern version of tort or orange, etc.
Tan pattern black (black otter)
Picture credit Sunny Slope Rabbitry
Tan pattern brown (chocolate otter)
Tan pattern black and non-extension (tort-black otter "fox")
Tan pattern black and chinchilla light (sable marten)
Picture credit Sunny Slope Rabbitry
a - Self
The most recessive allele on the agouti gene is self. Instead of eumelanin and pheomelanin pigment being switched on and off for different parts of the body, the eumelanin switch is simply always on (unless another gene interacts). Agouti and tan-pattern are the only alleles that will cause the "tan-pattern" ventral markings, so they are quite distinct. With some exceptions, lack of those tan-pattern markings indicates self if there is no white spotting preventing expression.
Self versus agouti or tan-pattern varieties include: black is is the self version of black otter or chestnut, chocolate is the self version of chocolate otter or chocolate agouti, siamese sable is the self version of sable marten or sable agouti, tort is the self version of tort otter or orange, etc.
Self black (black)
Self brown (chocolate)
Self black and non-extension (tort-black)
Self black and chinchilla light (siamese sable)
C “Color” Gene
The C gene controls whether pheomelanin pigment will be produced or not and also control whether expression of eumelanin pigment will be weakened or not. This gene has 5 (possibly 6) alleles with the recessive alleles having a co-dominant effect with each other. In the order of dominance, these include:
Full Color – C (wild-type)
Chinchilla dark – c(chd)
Chinchilla light – c(chl)
Himalayan – c(h)
Albino (REW) - c
There is a theoretical 6th allele, chinchilla medium, that would be in between dominance of chinchilla dark and chinchilla light. This has never been scientifically proven, so I have not included it here. I personally believe that it may exist or there may just be a wide range of modifier genes that drastically effect expression of chinchilla dark and chinchilla light.
Further reading: Aigner et al. 2000, Covrig et al. 2013
C - Full Color
The most dominant allele on this gene is the wild-type, full color. Quite simply, this allele allows the "full color" to be expressed as long as other genes aren't interacting (no effect). Any rabbit expressing pheomelanin pigment is full color.
Full color self black (black)
Full color black agouti (chestnut)
Full color self brown non-extension (tort-chocolate)
Full color tan pattern brown (chocolate otter)
c(chd) - Chinchilla dark
The next allele in dominance on this gene is the chinchilla dark allele. Chinchilla dark completely switches off pheomelanin pigment production and either does nothing to eumelanin pigment production, or weakens it slightly depending on modifier genes. So if other genes switched on pheomelanin expression (such as agouti), the chinchilla dark allele will switch that off (creating black and white bands in a chinchilla versus black and orange in a chestnut). The chinchilla dark allele may slightly affect the intensity of the eumelanin (weakening it slightly to a duller, slightly brown tone). So a black self chin versus a black may be slightly less intense in color (less jet-black). In Lionheads especially, modifier genes that weaken eumelanin expression in animals with the chinchilla dark allele are more intense, so "extremes" of highly weakened eumelanin expression are more common. An example of this would be a black self chin that has the black weakened so much that it more closely resembles a siamese sable than a black. In my opinion, this is where potential existence of a chinchilla medium allele could also be debated.
The chinchilla dark allele also SOMETIMES has a unique effect on eye color, known as marbling. Marbling is when both brown and blue-gray color is seen in the eyes in thin streaks which may be subtle or so dominant that the eye appears the opposite color for a dense or dilute. This can be associated with specific lines and many chinchilla dark animals do not express marbling.
Chinchilla dark is somewhat co-dominant with the more-recessive alleles on this gene in that a rabbit that is homozygous for chinchilla dark may be darker in eumelanin expression than one that is heterozygous for chinchilla dark. Because chinchilla dark often has very little effect on intensity of eumelanin expression in the first place, this co-dominant effect is very difficult to observe and often disputed for this particular allele.
c(chd)- expression in place of wild-type full color result in: black versus black self chin, chestnut versus chinchilla, chocolate versus chocolate self chin, tort-black versus sallander, orange versus ermine/frosted pearl, etc.
Chinchilla dark black agouti (chinchilla)
Picture credit Sunny Slope Rabbitry
Chinchilla dark blue agouti (squirrel)
Picture credit Sunny Slope Rabbitry
Chinchilla dark black tan pattern (black silver marten)
Picture credit Sunny Slope Rabbitry
Chinchilla dark eye marbling (gray streaks in a brown eye causing a dense color to appear to have blue-gray eyes)
c(chl) - Chinchilla light
Chinchilla light is next in dominance and works very similarly to chinchilla dark in that it completely switches pheomelanin pigment production off, but it additionally has a more intense effect in weakening of eumelanin pigment and affects the eyes differently. Chinchilla light is also co-dominant with the more recessive alleles on this gene with an effect that is drastically more visible than with the chinchilla dark allele above. A rabbit that is homozygous for chinchilla light has darker eumelanin expression than one that is heterozygous and homozygous chinchilla light alleles are known as "seal" versus heterozygous "sable" color. Modifier genes can greatly affect how much eumelanin pigment is weakened by the chinchilla light allele, causing a lot of inter-variety variation in animals with this allele as well as overlap in dark expression of homozygous and heterozygous animals.
The chinchilla light allele also uniquely affects eye color, causing reflective red ruby cast in the pupils of c(chl)- animals. I believe this to be caused by a reduction in pigment expressed in the epithelium of the eye, resulting in less light being absorbed by the pupil and therefore reflecting back. The only other allele that causes a similar effect is brown (chocolate) on the B gene, which was covered above. Modifier genes causing more weakening of eumelanin causes a stronger ruby cast because of less overall pigment. Likewise, homozygous (seal) animals with less eumelanin weakening have less ruby cast.
c(chl)- alleles in place of wild-type full color result in: black versus siamese sable, chestnut versus sable chinchilla, chocolate versus chocolate sable, tort-black versus sable point, orange versus sable-based ermine/frosted pearl, etc.
Chinchilla light self black (siamese sable)
Homozygous chinchilla light self black (seal)
Chinchilla light black agouti (sable chinchilla)
Picture credit Sunny Slope Rabbitry
Chinchilla light self black non-extension (sable point)
c(h) - Himalayan
Like the previous two alleles on the C gene, the Himalayan allele also completely switches off pheomelanin production. It also has a more drastic effect on eumelanin production, completely stopping all expression from most of the body (making it white) and from the eyes (making them red from visible blood vessels). This expression is highly temperature sensitive with less eumelanin pigment expressed the warmer the environment is. Eumelanin expression is usually limited to the "points" of the body (nose, ears, feet, and tail) which are the coldest extremities (with some exceptions such as dewlaps or other prominent folds of skin which tend to be colder). Since newborn kits are extremely sensitive to cold temperatures and unable to regulate their own body temperature well, they are commonly "chilled" at a young age (even in a temperature-controlled environment) and some eumelanin pigment gets expressed throughout the body as "frosted tips". Adult rabbits that can regulate their own body temperature rarely express eumelanin on the body no matter how cold it is unless they were to be missing fur on part of their body and get quite chilled. If kits are able to maintain warmth, somewhat reverse expression is seen at first with them often being born pure white and taking time to develop point color. Regardless of temperature or other genes interacting though, the eyes will always lack all pigment (red). The eye color sometimes has a slight bluish tone to it which is simply due to the color of the blood vessels and not actual pigment.
The Himalayan allele is highly co-dominant with the albino (REW) allele (below) which will cause highly decreased eumelanin expression in the points if carried.
c(h)- alleles in place of wild-type full color result in: black versus black pointed white, chestnut versus black pointed white agouti, chocolate versus chocolate pointed white, tort-black versus non-extension or "torted" black pointed white, etc.
Himalayan self black - (black pointed white)
Picture credit Ponder Lionheads & Netherland Dwarfs
Himalayan point intensity can be weakened by any other gene that modifies eumelanin expression
Picture credit Ponder Lionheads & Netherland Dwarfs
Himalayan point color can take time to come in.
c - Albino "REW"
The albino allele (called "REW" Ruby-Eyed White) is the most recessive allele on this gene and all other genes. It completely switches off all pigment expression period (eumelanin and pheomelanin) regardless of temperature or any other genes interacting. The coat and eyes completely lack pigment, causing them to be pure white with red/ruby/pink eyes. The eye color sometimes has a slightly blue tone which is simply due to the appearance of the blood vessels.
cc alleles in place of wild-type full color result in ruby-eyed white regardless of any other genes present.
Albino (ruby eyed white) pure white with ruby eyes regardless of any other genes
E “Extension” Gene
The extension gene controls expression of both eumelanin and pheomelanin pigmentation, but different than agouti does. This gene is very unique in how the various alleles function because some turn on eumelanin expression, some turn on pheomelanin expression, and some have co-dominant effects with each other.
(theoretical dominant black) E(D) - I will not be discussing this allele as it is disputed if it exists or not despite it being listed as an allele on this gene in some early scientific literature. Evidence I have seen presented for its presence cannot rule out steel E(s) as the cause, so I will assume that steel is the most dominant allele on this gene for the purposes of this material.
Steel – E(s)
Full Extension – E (wild-type)
Partial extension – e(j)
Non-extension - e
Further reading: Fontanesi et al. 2006, Fontanesi et al. 2010
E(s) - Steel
The steel allele is uniquely dominant to the wild-type allele and has complicated co-dominance with other alleles on this gene. Steel only has an effect on agouti or tan-pattern bases, not selfs because it requires pheomelanin pigment (specifically turned on by the agouti gene) to function. Where the agouti or tan-pattern alleles turn off eumelanin pigment production (such as in in ring color or on the belly), one copy of the steel allele turns the eumelanin production mostly back on except for the tips of the hairs. This causes a darkening of agouti banding and the ventral tan-pattern markings, making the rabbit appear closer to a self, but still leaving the tips expressing pheomelanin. Eye circles, ear lacing, and other tan-pattern markings are no longer distinct, though occasionally still show through slightly. When the steel allele is in homozygous form, the darkening occurs to such an extent that the entire hair shaft (including the tips) expresses eumelanin pigment and therefore agouti or tan-pattern markings are completely hidden and the animal appears self (known as super steels). Occasionally, modifier genes may allow for faint tipping to be seen in these animals. Phenotypic confusion may arise when steel offspring are born from parents that appear self, though this can be explained by the effect homozygous steel alleles have on hiding agouti banding.
Pheomelanin pigment expressed by non-extension is not affected by steel, however a very unique interaction between non-extension and steel has been reported by some breeders who report that E(s)e animals can look self even when they have an agouti or tan-pattern base on the agouti gene. Other breeders report that animals with this genotype look like normal steels, so it does not always function the same way and is therefore difficult to characterize. Non-steel agouti offspring from parents that appear self may be explained by this phenomenon as would many cases of reported "dominant black" genetics.
Black Gold-tipped Steel
Photo credit to Rebecca Mellor
Black Gold-tipped Steel
Photo credit to Rebecca Mellor
Remnants of ventral "tan pattern" markings can sometimes be seen such as under the nose in this rabbit, however the belly color and other markings are darkened to look similar as the rest of the body
Photo credit to Rebecca Mellor
Black Gold-tipped Steel French Angora
E - Full extension
Full extension is the wild-type allele on the E gene and simply allows full extension of the eumelanin pigment on the hair shaft. Pheomelanin pigment can only be expressed in full extension animals if the expression is turned on by agouti or tan-pattern on the agouti gene.
Full extension black agouti (chestnut)
Full extension black dilute self (blue)
Full extension brown tan-pattern (chocolate otter)
Full extension black agouti chinchilla dark (chinchilla)
Photo credit: Sunny Slope Rabbitry
e - non-extension
Note: I am skipping to the non-extension allele before describing the Japanese allele to make the complex Japanese allele easier to understand, though non-extension is the most recessive allele on the E gene.
Non-extension works by limiting the extension of eumelanin pigment on the hair shaft - causing an appearance of predominantly pheomelanin pigment. Eumelanin pigment remains on the "points" (the coldest parts of the body - nose, ears, feet, and tail) and lightly expressed at the tips of the hairs on the rest of the body. The intensity of the eumelanin expression is weakened, making black points more of a brown and brown (chocolate) points much paler than the pigmentation of their respective full extension colors. Modifier genes affect how much eumelanin pigment will remain on the body as well as the intensity of that pigment, leading to a lot of variation in "shading" of non-extension varieties. Other genes that limit eumelanin expression will have an subtractive effect to eumelanin pigment expression when combined with non extension such as agouti+non-extension producing colors such as orange which have less eumelanin expression than the respective non-extension self variety, tort-black. Alleles on the C gene that turn off pheomelanin production will leave white coat color in place of red-yellow when combined with non-extension such as tort-black versus sable point or orange versus ermine.
Non-extension black agouti (orange)
Non-extension black self (tort-black)
Non-extension blue self chinchilla light (smoke pearl point)
Non-extension black agouti chinchilla dark (ermine/frosted pearl)
Photo credit: Mountain Ledge Lionheads
e(j) - Japanese
Because of the complexity of this allele, I am listing it last, though it is the second to last allele on the E gene according to dominance.
The Japanese brindling allele is particularly complex in its function and inheritance. In heterozygous form, this allele switches on eumelanin pigment randomly to some hairs (that other genes allowed pheomelanin pigment expression in) while leaving other hairs intact. The hairs with additional eumelanin expression tend to be clumped together in bars or bands typical of harlequin coloration, though can also be fairly evenly dispersed to more of a brindled appearance. This marking in heterozygous form can occur in Ee(j) animals such as chestnuts, chinchillas, otters, or martens (the allele combination often known as "harlequinized) showing darker markings especially in the ventral tan-pattern markings, in eje animals such as tort-blacks (the allele combination often known as "torted" harlequin) showing darker markings in addition to the normal shaded appearance of non-extension, or even in E(s)e(j) animals faintly showing patches of the coat missing steel tipping. In self aaEe(j) animals (such as blacks, blues, etc), the Japanese allele has no effect since the eumelanin production "switch" is already on. Common locations of Japanese markings are split color on the face, one ear or leg darker than the other, or bands/bars/brindling on the belly and body.
In homozygous form, the Japanese allele not only switches on eumelanin expression to some hairs, but it also switches on pheomelanin production to the other hairs. The Japanese allele does a "better" job of expressing pheomelanin pigment than non-extension does, because it expresses it over the entire hair shaft rather than how eumelanin remains on the points of the body and tips of the hairs in non-extension animals. When comparing an ee(j) torted Japanese harlequin to an e(j)e(j) Japanese harlequin for example, the torted harlequin will have eumelanin "left behind" by non-extension in the points and faintly throughout the body in addition to the eumelanin markings added by the Japanese allele, causing a muddy "torted" appearance which takes away from the appearance of clean color borders. In contrast, the e(j)e(j) Japanese harlequin has clean color borders due to pheomelanin-expressing-hairs not also expressing some eumelanin. A more-brindled type pattern will make this harder to distinguish though. This co-dominant effect with non-extension can be seen in an agouti, tan pattern, or self base, though it is better hidden in an agouti base, due to the additional minimization of eumelanin expression by agouti banding.
When combined with chinchilla dark or light alleles that switch off pheomelanin pigment, orange markings become white. This is known as magpie coloration.
Left to right: Japanese, magpie, Japanese
"Split" face marking of additional eumelanin expression on "torted" blue Japanese
Harlequinized chinchilla (note additional eumelanin expression in "split" face marking and "muddying" of the belly color. Photo credit KC's Little Paradise
En “English Spotting” Gene
English spotting is the most common white spotting gene in rabbits with spots of fur that are completely missing all pigment (eumelanin and pheomelanin). The English spotting gene includes the wild-type allele which has no effect and is recessive to the English spotting allele which is incompletely dominant. Wild type rabbits e(n)e(n) are solid, heterozygous E(n)e(n) animals have various degrees of white spotting (known as broken patterning), and homozygous E(n)E(n) animals have a high degree of white spotting and minimal coloration (known as Charlies due to common marks on their upper lips that resemble Charlie Chaplin's mustache). English spotting affects the migration pattern of pigment cells from the neural crest causing parts of the body to lack any pigment. Although the markings vary in amount of color present (heavy color is known as booted, medium color is known as blanket or spotted pattern, and heavy white is known as Charlie, or false Charlie), the general location and shape of the markings are predictable. Minimally, the belly and legs are marked with white and the face tends to have white markings outlining a "butterfly" shape of color. The ears and around the eyes are almost always colored and a colored stripe down the spine is also commonly present (if not a larger marking over the back) with markings being round in general shape.
Homozygous English spotting alleles (Charlies) have been linked with incidence of megacolon, although not all Charlies have this condition. Because of this, breedings that can produce Charlies are often avoided. Heavy white patterning can be present in heterozygous animals due to modifier genes, and these are known as "false Charlies".
English spotting has a unique epistatic interaction with the Japanese allele on the E gene causing the Japanese markings to be round rather than bars/bands or brindling as typically seen in the solid form of the variety. This is likely a result of how English spotting affects migration of pigment when it is clustered together to form spots.
White Ear is thought to possibly be an allele on the English Spotting gene, though is not well characterized yet and may be a separate gene.
English Spotting – En
No English Spotting – en (wild-type)
Possibly WE dominant to wild type
Further reading: Fontanesi et al. 2014
Other white spotting genes can express at the same time as English Spotting. Classic blaze markings produced by Vienna can make the classic colored nose marking in English Spotting disappear.
Medium to heavy white markings in English Spotting tend to minimally leave a stripe of color down the spine. Markings tend to be round in shape.
Heavy or light white markings can appear within a single litter.
Light white markings
V “Vienna” Gene
There are two alleles on the vienna gene - wild-type V and the vienna allele v. The vienna allele produces an incomplete form of albinism in homozygous form, causing a pure white body with no pigment expression and ice blue eyes. The body is pure white because all melanin is restricted from melanocytes that originate in the neural crest. Melanocytes originating outside of the neural crest can still produce melanin which allows for blue eyes instead of ruby (pigmentless) eyes. In the eyes, pigment is restricted in the stroma and only remains in the epithelium.
The vienna allele has incomplete dominance, so heterozygous animals (Vv) may express both alleles at the same time such as normal coloration determined by the other genes present while also expressing marks on the body that are void of pigment (white) or in the eyes where pigment is restricted to the epithelium (blue spots). When these markings are present in a heterozygous animal, it is called "vienna-marked" or "VM". Sometimes heterozygous animals do not express any markings from the vienna allele and these are known as "vienna-carriers".
Homozygous vv animals will always be blue-eyed whites in appearance unless they are also c(h)- or cc on the C gene, in which case they will be ruby-eyed whites in appearance. This is because the himalayan and albino alleles will completely switch off all pigment in the eyes including in the epithelium.
The phenomenon of "ruby cast" in the eyes of animals expressing brown (chocolate) or chinchilla light (sable), will show through in BEWs with a bb and/or c(chl)- genotype. Because BEWs only have pigment in the epithelium of the eye, I believe that the brown and chinchilla light cause a reduction of that pigment, resulting in less light being absorbed by the pupil and therefore reflecting back.
Non-Vienna – V (wild-type)
Vienna – v
Further reading: Proorocu et al. 2019, Aigner et al. 2000
Homozygous vienna alleles
Vienna markings can extend to the eyes, leaving ice blue color
Vienna markings can sometimes mimic Dutch markings
Left to right: ruby eye, blue eye with ruby cast caused by chinchilla light, blue eye
W “Wideband” Gene
Wideband in general is poorly understood, though most commonly discussed in reference to red color. Wild-type is dominant and results in no effect and wideband is recessive, causing a widening of the intermediate band (the band of pheomelanin) in agoutis. In full extension agoutis like chestnuts, this creates the appearance of shorter black tips (eumelanin) and more red (pheomelanin) and wideband chestnuts are often called copper to distinguish them. In colors where pheomelanin pigment is not present, such as chinchillas, the intermediate band is still widened, resulting in more white appearance to the overall color, sometimes called "ghost chinchilla". When in combination with non-extension, darker tips of "smut" are reduced. Wideband also has an effect on the ventral "tan pattern markings" of agoutis and tan-pattern varieties, causing increased pheomelanin expression instead of white. This causes the belly color and other tan markings to be cream to red (instead of white) depending on rufus modifiers and tends to widen their coverage on the body as well.
Non-wideband – W (wild-type)
Wideband - w
Wideband agouti, non-extension (red)
Widening of the intermediate band reduces visible smut
Wideband causes increased pheomelanin in the belly and other tan pattern markings, causing them to be more cream/red than white
Rufus modifiers control whether tan pattern markings will be cream to red
Du “Dutch” Gene
The Dutch gene is believed to include the wild-type allele which has no effect, the Dutch dark allele which is incompletely dominant and produces white markings associated with typical Dutch patterning and the Dutch white allele which produces white markings to a greater degree and is associated with Hotot coloration when combined with English Spotting. Anther theory is that there is simply a wild type allele and a Dutch allele and the variation in white is controlled by modifier genes. In heterozygous form, minimal white markings are often expressed very similarly to vienna, with small blazes or white foot markings often expressed or no white markings at all. In homozygous form, white markings are consistently produced, though exact placement of white markings as outlined by the Dutch standard of perfection are a result of careful selection for modifier genes that produce similar markings, though small variation in markings is still common in litters. Dutch can also sometimes mark the eyes resulting in ice blue eyes like vienna.
Non-Dutch – Du (wild-type)
Dutch dark – du(d)
Dutch white - dd(w)
Further reading: Punnett and Pease 1925, Castle 1926, Castle 1934, Castle J of Experimental Zoology 68(3), Rifaat 1953
Si “Silver” Gene
Silvering in rabbits is mostly breed-specific with breeds like the Silver Fox, Champagne d'Argent, Creme d’Argent, and Argent Brun expressing it and very few non-silver breeds having the silver allele present in the common gene pool. This gene is quite complex and difficult to characterize. The silvering allele behaves in a co-dominant manner, with one copy of the gene causing some hairs to be white at the tips and two copies causing increased expression (more hairs expressing white tips). The white tips often take time to develop with young animals often not showing any tipping until the coat matures. The nose, around the eyes, ears, feet, and tail tend to express less tipping. There is a lot of debate surrounding what causes the extremes of expression (such as the notable difference in appearance between Silver Fox and Champagne d'Argents) with some believing there are 2-3+ silver genes (notated as S(1), S(2), and S(3)), while others suspect that the variation is caused by modifier genes. Stray white hairs are often confused for silvering genetics and are also commonly present in silver breeds because they "hide in plain sight".
Silver – S(i)
Non-Silver – s(i) (wild-type)
P “Lutino” Gene
Lutino is a form of albinism, where eumelanin pigment is limited from the coat and eyes and pheomelanin pigment remains mostly unchanged. The eyes look pink or pink/purple because they have very little pigment expression, though there is some present which contrasts them from true ruby eyes seen with c(h) or c genetics. Depending on the interaction of other genes, this often causes "red-eyed red" color appearance. Lutino genetics are quite rare in the US at this point, but there are breeders working on developing the color in several breeds. I do not have first-hand experience with lutino genetics, so please check out http://www.kaninchenwissen.de/knowledge/kb_show.php?id=34 for good further reading on the gene.
Non-Lutino – P (wild-type)
Lutino - p
Other Genetic Factors on Coat Color
Rufus factor is the name for additive modifier genes that control how intense pheomelanin pigment is. Low rufus results in lighter, more fawn expression and high rufus results in a more intense, red-orange expression.
Snowballing is not well understood, but appears to affect predominantly dilute colors, but is also known to affect dense colors to a lesser degree. Mild snowballing appears as stray white hairs in the coat of junior animals that goes away with age or slightly diffused undercolor. More severe snowballing appears as white undercoat that can extend far up the hair shaft (with or without stray white hairs) , but also goes way with age. In my experience, snowballing in dense colors like black tends to appear as a few white hairs in the whisker bed that also go away with age.
Stray White Hairs
Stray white hairs can appear in any variety, but are more noticeable in darker, more solid colors like full extension selfs. These tend to come in with senior coat and can gradually increase in number of white hairs with age. The inheritance for stray white hairs appears very additive in nature, so selection for the least stray white hairs in a breeding program will help to minimize its presence in future generations. Some populations of rabbits tend to hide stray white hair genetics if they are colors that are white or light such as REWs, brokens, or sable points and crossing these populations with other colors can make the stray white hairs more visible in resulting generations.
Random White Spotting
Some breeders report the presence of random white spotting genetics that are distinct from English spotting, vienna, or Dutch. These are difficult to characterize, but can appear as white nose snips, white feet, or other markings similar to vienna.