Rabbit color genetics can be incredibly overwhelming when you are first introduced to them! We have spoken with Sarah Hallgren of Toki Doki Rabbitry to bring you an overview of rabbit color genetics and give you a foundation to learn from. After we introduce Sarah we will lay down the fundamentals of genetics and then discuss the A, B, C, D, E, and En loci.
More About Toki Doki Rabbitry
Toki Doki Rabbitry is located in Texas and they breed mostly Rex rabbits. Sarah started raising rabbits with the intention of using them on the homestead and as future show projects for her children.
She started with show-quality breeders and soon became interested in rabbit color genetics. Sarah has started a few color projects because of this.
Fun fact: Toki Doki is a play on words in Japanese and Korean, which are two languages Sarah speaks. “Ttoki” means “rabbit” in Korean and “toki doki” means “every now and then” in Japanese. Sarah says, “The idea is ‘Rabbits every now and then’ but it’s grown to be more like rabbits all the time.”
The Fundamentals of Rabbit Color Genetics
Before we dive in we’re going to take a quick trip back to high school biology!
Definitions of Common Genetic Terms
- Genetics – The study of heredity and the variation of inherited characteristics. Fur color genetics are the most common when discussing rabbits.
- Allele – One of two or more alternative forms of a gene that arise by mutation and are found on the same place on the chromosome.
- Locus / Loci – The specific physical location of a gene or other DNA sequence on a chromosome, like a genetic street address.
- Dominant – Dominant genes can visibly be seen and are noted with a capital letter (A, B, C, etc.). They always override recessive genes in terms of appearance.
- Recessive – Recessive genes can not be seen, but they can be passed on to offspring. These genes are noted with lowercase letters (a, b, c, etc.).
- Homozygous – An identical pair of genes (homo = same). Example: AA or bb.
- Heterozygous – Two different genes (hetero = different). Example: Aa or Bb.
- Phenotype – Physical characteristics of which can be seen with the eye (a blue coat color).
- Genotype – The genetic code, which can not always be outwardly seen (AaBbCcDdEe).
The Basics of Rabbit Color Genetics
Each kit receives ½ of each parent’s genes. Below is a chart showing the heredity percentages of kits. Both dominant and recessive genes are passed on to roughly half of the offspring. They get two genes from each locus, one from each parent. If there are more than two variables on the locus each rabbit still will only receive two.
Parts of the rabbit’s genetic code that are unknown are killed with an underscore (AaB_c_DDEEnen).
The 5 gene locations act on only TWO colors in the rabbit’s coat. Black and yellow. Some genes produce a color and some genes “turn off” a color.
Rabbit Color Genes
The loci are explained in decreasing order of dominance.
“A” Locus
Each rabbit can only show one “A” gene. This is usually the easiest rabbit color genetic to determine.
“A” – Agouti
Agouti is the most dominant gene in the “A” locus. Sarah states, “Agouti rabbits have different colors on the hair shaft. Usually a base color, middle ‘ring’ color, and then the top color”.
Common varieties of agouti-colored rabbits include castor, opal, amber, and lynx. These rabbits have lighter fur around their stomach, eyes, tail, and inside of their ears. You can see this color difference when the kits are born, but they may be mistaken for otters before their fur starts to grow.
Sarah also says, “Black agouti (castor) is the most dominant color and that is why we see it a lot in wild animals”.
Common agouti colors:
- Castor – Black agouti
- Opal – Blue agouti
- Amber – Chocolate agouti
- Lynx – Lilac agouti
Agouti rabbits can be AA, Aat, or Aa. Agouti (A) is dominant and therefore hides the recessive genes of at and a.
“at” – Otter
The “at” gene is recessive to “A” but dominant over “a” (self). It is responsible for the otter, marten, and tan colors. These rabbits have a tan or white color on the stomach, inside of the ears, and around the eyes and nose.
Black, blue, chocolate, and lilac colors can all come in the otter variety.
“at” rabbits with chinchilla, seal, or sable genes and an “E” (full extension) gene would be considered martens (more on that later in the article).
Otter rabbits can be atat and ata. Otter is dominant over self and can hide the recessive self gene.
“a” – Self
“a” is the most recessive gene in the A locus. It is responsible for a consistent color throughout the entire body and along the hair shaft.
Mink Hollow Rabbitry states, “Other alleles can affect the way this is expressed – most commonly with either the top coat extending well down the hair shaft, as in Steel, or the midband extending outward to the tips (as in non-extension). As a result of this, the longer hairs of the animal often end up appearing to be a different color from the shorter hairs.”
Common self varieties include black, blue, chocolate, and lilac.
Seal, sable, and Californian colored rabbits also carry aa (self).
A self rabbit can only be aa because it is the most recessive gene in the A locus. Both the A and at genes will hide a, the self gene.
“B” Locus
There are only two options on the “B” locus – black and chocolate. All rabbits fit into one of these two categories.
“B” – Black
Black (B) is dominant on the “B” locus.
Varieties include black (self), blue, castor (black agouti), and opal (black dilute agouti).
Black rabbits can be BB and Bb. If a rabbit is Bb it will hide the recessive chocolate gene.
“b” – Chocolate
Chocolate (b) is recessive in the “B” locus, meaning a rabbit has to be bb to present as chocolate.
Chocolate, lilac, amber (chocolate agouti), and lynx (chocolate dilute agouti) are all varieties of bb.
“C” Locus
Things start getting a bit more complicated on the “C” locus. The “C” genes are responsible for varying degrees of shading and affect melanin production in the hairs. It is the most difficult locus to understand because some genes are incompletely dominant over others. You may also find it interesting that the “C” gene is temperature sensitive.
“C” – Full Color
The “C” gene creates consistent coloring over the rabbit’s entire body. Sarah says “C” is arguably the most common among the C genes. (Broken rabbits can be full color too.)
Common varieties of the “C” gene include black, blue, and castor.
Full-color rabbits can be CC, Ccchd, Ccchl, Cch, and Cc, this is because the “C” gene is dominant over all other genes on the “C” locus.
“cchd” – Chinchilla
Phenotypically, the chinchilla gene is almost indistinguishable from full-color self rabbits. Sarah says, “A self chinchilla rabbit will look just like a full self-color rabbit, except they may have grey-blue eyes or have a rusty tinge to their fur.” The chinchilla gene has also been shown to extend the white pattern on a broken rabbit up past the ear base.
“cchd” stands for “chinchilla dark” and it changes most yellow pigment to white or pearl.
Chinchilla, silver marten, and sallander rabbits are a few that carry cchd.
The cchd gene is recessive to C and dominant over ch and c. That means cchdcchd, cchdch, and cchdc are possibilities for rabbits carrying the chinchilla gene.
“cchl” – Sable
“cchl” stands for chinchilla light, which may sound similar to chinchilla dark, but they are quite different. The sable gene reduces most of the yellow to white just as the cchd gene does. But, the cchl gene also gives the rabbit a shaded look and the eyes stay dark in color, unlike cchd.
The sable gene also reduces black pigment, but typically leaves the head, legs, ears, and tails a darker shade. This can change due to temperature and coat conditions. Rabbits carrying the cchl gene often look darker brown than black. The difference between a sable and a chocolate is comparable to dark vs milk chocolate.
cchl is recessive to C and cchd, but incompletely dominant over ch and c.
Mink Hollow Rabbitry states, “The shaded allele is not fully dominant over the next two (ch: Himalayan, and c: red-eyed white), so the results may look different depending on the second allele. The difference can be quite subtle”. They also say, “A ‘true’ or genetic seal is a self that is homozygous for the shaded allele”, meaning cchlcchl on the “C” locus.
Some varieties of rabbits carrying cchl include sable, seal, and smoked pearl.
Sable rabbits can genotypically look like the following:
- Cchlcchl – “true” seal
- Cchlch – Sable
- Cchlc – Sable, but the dark points become lighter, the difference can be subtle.
“ch” – Californian or Himalayan
The “ch” gene is responsible for Californian (or Himalayan dependent on the breed) colored rabbits. These rabbits have red eyes and they develop points (darker fur) on their ears, feet, and tail as they age. The points are temperature sensitive. During the hot times of the year, the points on a ch rabbit can and will fade.
Sarah states, “As a temperature-dependent variety, smut is an issue where dark coloration shows up on the back or other areas that should remain white.” The colored parts on a Californian rabbit are the coolest part of the body. This “smuttiness” occurs most commonly on the back and dewlap, the next coolest parts of the body, and is most common if the rabbit is not homozygous.
ch is recessive to C, cchd, and cchl, but is it dominant over c.
The Californian gene can show as chch or chc. But remember, the rabbit will have more clear points if it is homozygous (chch).
“c” – REW
REW stands for ruby-eyed-white and for REW to show phenotypically, it has to be homozygous – cc. The cc gene negates whatever the other loci are contributing to the rabbit’s color. Meaning, cc basically acts as a snow-white blanket, covering all of the genes that lie beneath it.
The REW gene is completely recessive and will not be present in any form other than cc. So, you know both parents carry c, whether that be in the dominant or recessive form.
A REW rabbit could genetically be self black, but it will phenotypically present as a white rabbit with red eyes. In order to figure out the rabbit’s genetic code you will have to strategically breed and eliminate possible genetic codes.
REW is only possible with cc, all other genes on the “C” locus are dominant over it.
“D” Locus
This is the dilute locus which is responsible for changing black to blue and amber to lynx.
“D” – Dense
“D” is the dense gene and it is dominant. These rabbits do not have any dilution.
Some examples of rabbits carrying “D” include black, castor, and chocolate.
Dense rabbits can either be DD or Dd.
“d” – Dilute
Dilute rabbits are basically the lighter version of the dense color. They have to carry dd because d is recessive to D. If you have a litter with dilute kits you know both parents carry d.
Blue, opal, and lilac rabbits are varieties of the dilute gene, all of which carry dd.
“E” Locus
The “E” gene affects whether the basic color of the rabbit extends all of the way to the end of the hair shaft or whether the basic color stops and another finishes the hair shaft.
“Es” – Steel
Es is the most dominant of the “E” genes and it is responsible for steel and all other steel variances. Sarah says, “Steel is a tricky gene that reserves the color order on the hair shaft and you can see black bellies instead of white on agouti or otters”.
The Es gene covers the middle band color in an agouti (A_) coat by carrying the dark pigment mostly up the hair shaft. This gene can hide if the rabbit is not agouti. Since otter and self rabbits already have single-colored hair shafts, there is no light color at the end for the steel gene to leave.
Rabbits carrying Ese will either have steel or gold-tipped fur.
Es is dominant over E, ej, and e.
EsEs, EsE, and Ese are possible genetic combinations.
“E” – Full Extension
Rabbits that carry full extension are the same color along the whole hair shaft, like a lilac rabbit. E is the most common gene in the “E” locus.
If a rabbit carries E they will not have any extra patterning on the hair shaft (like blue, chocolate, etc.), most rabbits are EE. The E gene does not affect the broken gene (En).
This gene has partial dominance and if a rabbit is heterozygous on the “E” locus the recessive gene can sometimes show through. An example of this is a harlequinized castor (Eej).
Some common varieties are castor, black otter, and blue.
E is recessive to Es and partially dominant over ej and e.
Possible genetic variations include EE, Eej, and Ee.
“ej” – Harlequin/ Tri-color
The harlequin gene, ej, produces a brindled pattern that can include black, blue, chocolate, and lilac harlequin or magpie. Black tipping appears in patches, somewhat similar to a calico cat.
Harlequins with a red under color carry C on the “C” locus and magpies with a white under color carry cchd, the chinchilla gene, on the “C” locus.
An agouti (castor, opal, amber, etc.) or an otter that carries one full extension gene (E) and one harlequin gene (ej) will always show the black patches, most noticeable around the eyes and on the inside of the ears. These rabbits are called harlequinized otters, harlequinized ambers, etc.
The ej gene paired with the En gene produces a tri-color.
This gene is recessive to Es and E, but dominant over e.
ejej and eje are possible genetic combinations.
“ee” – Shading or Non-extension
ee is the most recessive among the “E” genes. This gene is responsible for tortoiseshells, reds, fawns, etc.
The short hairs (on the stomach, feet, and muzzle) get only the basic color because the hairs are not long enough to get the other color.
A self colored rabbit that carries ee will appear as a tortoiseshell, and an agouti colored rabbit that carries ee will not have the necessary ticking which in turn creates reds and creams.
Some common examples of rabbits carrying ee include red, fawn, tort, and sallander.
e is recessive to Es, E, and ej.
The only possible gene combination is ee.
“En” Locus
The broken gene. This gene can overlap any of the genes mentioned previously. The broken gene is on top of all other genes. Think of it like dipping a colored rabbit in white paint.
There are two genes in this locus: En (broken) and en (not broken). En is dominant.
“En/En” – Charlie
These rabbits have 2 broken genes and are almost all white, with barely any color showing (less than 10%). Charlie is created by breeding two broken rabbits.
“En/en” – Broken
10-90% of color. In order to create broken offspring, one parent has to be broken. You can not get a broken kit from two solid parents.
“en/en” – Solid
This is when the entire rabbit is colored. Even the otter class and agouti class with white stomachs fit into this category.
Conclusion
Hopefully, you now have a better understanding of the A, B, C, D, E, and En loci, as well as how they play off of each other. In the future, we will be writing more articles about the modifiers that can affect the loci explained above. Rabbit coat genetics can seem so overwhelming when you are trying to translate a live animal into letters, but with a little time and studying, you will catch on!
