Basic Rabbit Genetics
Chromosomes, Genes, Alleles, and Loci
Chromosomes are strands of DNA that act as a map. They map out exactly how the rabbit will look. In each cell, not including the sex cells and red blood cells, a rabbit has 22 chromosomes. Each chromosome has one "slot" per gene, and since chromosomes come in pairs, there are two "slots" total. Alleles are versions of genes which can differ from one another. Commonly people call them genes, but genes actually encompass all possible variants. A locus (plural: loci) is the physical location of a gene on the chromosome, or the "slot" that an allele can fill. In the two slots, an allele may be the same, or they might be different, but there are always two (unless there is a genetic mutation, but we will not discuss that here). For example, a rabbit might have two alleles for blue eyes. Conversely, a rabbit might have one alleles for red eyes, and one allele for brown eyes.
If a rabbit has two of the same type of alleles in a certain chromosome pair, it is referred to as being homozygous for that particular allele. If it has two different genes in a certain chromosome pair, it is referred to as being heterozygous.
If a rabbit is heterozygous, one of the alleles is usually stronger than the other. That means that the stronger allele will be the one to cause the effect in the rabbit, and the weaker one will just hide, though it can still be passed on to the rabbit's offspring. Stronger alleles are referred to as being dominant, and weaker alleles are called recessive. For example, if a rabbit had one allele for red eyes and one allele for brown eyes, the rabbit would have brown eyes because the allele for brown eyes is dominant to the allele for red eyes. For a rabbit to have red eyes, it would have to be homozygous for red eyes, since the allele for red eyes is the most recessive.
Sometimes certain alleles are not really stronger or weaker than another. These alleles are referred to as being incompletely dominant to each other. This means if two different alleles that were incompletely dominant to each other were in the same rabbit, the rabbit would have traits from both alleles. In flowers, and example of an incompletely dominant allele can be found when you breed a white flower and a red flower and you get a pink flower. In rabbits, an example of this is broken. One copy of the broken allele makes normal broken, two copies make 'charlie' marked rabbits, and no copies make solids.
Color Alleles
Each variety of rabbits requires many alleles of many genes to look the way they look. You may have seen some genetics stuff written with a bunch of ABC's and other letters. Well, those are how various loci and alleles are written. Genes have their own alphabet. When the "letters" of the genetics alphabet are all put together, it is referred to as the rabbit's genotype. This is basically a list of all the colour alleles that rabbit has, or at least the ones that are important to understanding that particular variety.
Genotypes
In order to have a full knowledge of the variety of a rabbit, just by looking at the genotype, a full genotype, using all of these loci. For example, a Chestnut Agouti would be denoted as A_ B_ C_ D_ E_ enen V_ W_ Si_ Du_. The spaces just mean that a recessive allele could be there, hidden by the dominant allele. However, most people know that the shortened form of the genotype, A_ B_ C_ D_ E_ enen, also means Chestnut Agouti. We are thankful for this as it saves us a lot of typing and writing. :)
A LOCUS
The first "letter" in the genetics alphabet is "A." This determines the basic pattern of the rabbit. The alleles are as follows:
A: Agouti Pattern - These rabbits have tan, white, or fawn markings on the belly, underside of the tail, inside of the feet and legs, inside the ears and nostrils, around the eyes, and in the shape of a triangle at the nape of the neck. On the body, the fur has rings of different colors when you blow into the coat. Example above: chestnut agouti.
aᵗ: Tan Pattern - Like agouti pattern, these rabbits have tan, white, or fawn markings on the belly, underside of the tail, inside of the feet and legs, inside the ears and nostrils, around the eyes, and in the shape of a triangle at the nape of the neck. However, the body does not have the different color rings when you blow into the coat. Example above: silver marten.
a: Self Pattern - Each hair is a solid color, and there are no tan, white, or fawn markings. Example above: black.
B LOCUS
"B" is the next "letter". This "letter" tells the rabbit how intense the color of the fur is. The alleles are as follows:
B: Black - The rabbit is black based, meaning the base color is black or blue. Example above: black based magpie harlequin
b: Brown - The rabbit is brown based, meaning the base color is chocolate or lilac. Example above: chocolate (brown) based magpie harlequin.
C LOCUS
"C" is the next "letter". This "letter" tells the rabbit whether or not to have red-orange color, as well as how deep and dark the base coloring is. The genes are as follows:
C: Full Color - The red coloration of the fur is full expressed, and the base coloring is also fully expressed. Example above: chestnut agouti.
cᶜʰᵈ: Chinchilla Dark - All red coloration is removed from the coat, but the base coloring is still fully expressed. Example above: (broken) chinchilla.
cᶜʰˡ: Chinchilla Light - All red coloration is removed from the coat, and the base coloring is lightened, causing darker shading around the head, ears, tail, feet, and legs. Example above: sable silver marten.
cᶜʰ: Himalayan - All red colouration is removed, and the base colouration is restricted to the nose, ears, feet, legs, and tail. The eyes are red. (Also known as 'Californian' or 'Pointed White'). Example above: Californian
c: Albino - All color is restricted, leaving a pure white rabbit with red eyes. Known as "ruby eyed white" or "REW". Example above: ruby eyed white.
D LOCUS
Next in the genetics alphabet is "D". This "letter" determines how much pigment is in each hair shaft. The less pigment there is, the lighter the colour is. The alleles are as follows:
D: Dense - Full amount of pigment. Example above: black silver marten.
d: Dilute - The pigment is less, causing the color to look diluted. Example above: blue silver marten.
E LOCUS
The "letter" "E" controls the banding, or color rings (remember in agoutis where you can see the rings when you blow into the coat?) of a rabbit. The alleles are as follows:
Eˢ: Steel - The undercolor is extended and "takes over" the color, leaving a mostly solid colored rabbit with some gold or silver tipped hairs. Steel works on the red or white areas of the rabbit, so in self rabbits (where there is no visible red or white), steel is not visible. Example above: steel.
E: Full-Extension - The rabbit has normal color, and the bands are not disturbed. Example above: chestnut
eʲ: Japanese - This takes the bands and actually seperates the band colour into different hair shafts. This is how Tricolor and Harlequin are produced. Example above: magpie harlequin
e: Non-Extension - There is no colour extension, leaving only what would be the intermediate band in a normal coloured rabbit. This is how Oranges, Frosed Pearls, and Tortoises are produced. It essentially removes most to all of the black-brown pigment. Example above: orange
EN LOCUS
The "En" "letter" controls a different type of pattern. The alleles are as follows:
En English Spotting - The rabbit is white with colored spots. Example above: broken black.
en: Solid - The rabbit has no spots. Example above: black
EnEn (two copies of English Spotting) makes a different color! Charlie is more white than regular broken. Example above: charlie black.
V LOCUS
"V" is the next "letter" in the genetic alphabet, and for most breeds, no more of the alphabet is needed to know the variety. This tells whether or not the rabbit is a Blue Eyed White.
V: Non-Vienna - Normal colored rabbit. Example above: non-Vienna blue tort.
v: Vienna - Blue Eyed White. Example above: blue eyed white (BEW)
Vv (one copy of Vienna) sometimes makes a different color! Vienna marked rabbits have white markings similar to Dutch and often have blue eyes. A rabbit can be Vv and not be Vienna marked. Example above: Vienna marked harlequin.
W LOCUS
This "letter" is rarely included in the genotype because it is not very important in most varieties, though all varieties DO have it either in the Non-Wideband or the Wideband allele.
W: Non-Wideband - Normal coloring. Example above: chestnut.
w: Wideband - The intermediate band widens, undercolor on the belly is white instead of colored. Wideband seems to be closely linked with color intensity, and wideband often produces deeper, richer red coloring due to this. Example above: wideband agouti.
SI LOCUS
This "letter" is another that is rarely included in the genotype. All non-silver rabbits do not need this included in their genotype in order to let the viewer know that the rabbit is not silver.
Si: Non-Silver - Normal coloring. Example above: black
si: Silver - Silver-white hairs are scattered throughout the normal coloring. Example above: silvered black.
DU LOCUS
This "letter" is usually only used when referring to the breeds Dutch, Dwarf Hotot, and Hotot. Dutch white markings also exist in the Harlequin breed because Harlequins derived from Dutch.
Du: Non-Dutch - Normal coloring.
du: Dutch - Dutch markings.