Rabbit Coat Color Gene C

Although there are five main color genes than determine the color of a rabbit's fur, the c-family of genes is called the "color gene."  The color gene, which controls where  and how much color will be expressed rather than which color will be expressed, is definitely the most difficult to understand.  The first complication is that there are more variations of this gene than of any other color gene.  Another complication is that some genes are incompletely dominant over others.  But in spite of its complications, it is one of the most fascinating genes to work with. 

 

Let's start by thinking about which types of colors are produced when the different color genes are expressed.  The dominant color gene is the "Full Color" gene represented by the capital "C."  Some full color rabbits are black, orange, chestnut, black tortoiseshell, lilac, and blue.  The next gene, in order of dominance, is the chinchilla gene, which is represented by the letters chd (or sometimes Cchd or c_chd).  The letters stand for "chinchilla-dark."  You won't be surprised to find that the chinchilla rabbit has the c_chd gene.  Other rabbits such as ermine, squirrel, chocolate chinchilla and lilac ermine also have the c_chd gene as the dominant color gene.  The next gene is the sable gene represented by c_chl, which stands for "chinchilla-light."  Smoke pearl and sable point are examples of rabbits with the chl as the dominant color gene.  Himalayans have the ch (or c_h) gene while ruby-eyed whites (REWs) have two "c" genes.

 

What's Going On Genetically

 

Beginning with the most dominant and ending with the least, the color genes are "C," which is the full color gene, "c_chd," which is the chinchilla gene, "c_chl," which is the sable gene, "c_h," which is the Himalayan gene, and "c," which is the REW or albino gene.

 

The Full Color Gene -- The full color gene is expressed anytime it is present.  There are five combinations of genes that will cause a rabbit to be "full color."  A full color rabbit may be "C-C," "C-c_chd," "C-c_chl," "C-c_h," or "C-c."  In full color rabbits, the color is not restricted to a certain part of the rabbit, but it spread over the entire rabbit.  Other genes, such as the ee genes may cause a shaded look in a full color rabbit, but the color restriction is not due to the "C" gene in that case.

 

The Chinchilla Gene -- The Chinchilla gene (c_chd for chinchilla-dark) will be expressed if paired with any gene but the full color "C" gene.  Chinchilla rabbits can be either "c_chd-c_chd," "c_chd-c_chl," "c_chd-c_h," or "c_chd-c."  When the chinchilla gene is expressed in rabbits, you generally find white or pearl fur where the full color rabbit has more yellow in the fur.  The  c_chd gene causes the yellow pigment to be reduced.  For example, an orange rabbit differs from an ermine (frosty or frost point) only in that the orange is a full color rabbit and the ermine expresses the chinchilla gene.   Once the yellow pigment is eliminated from the orange, only the pearl remains.

 

It is worthwhile to note that the best chinchilla colors are produced with either a REW or Himalayan gene under the chinchilla gene rather than a sable gene.  The sable gene tends to muddy the color, due to its incomplete dominance/recessive nature (more below on that).

 

The Sable Gene -- With the sable gene (c_chl), we find a slightly different situation than with other genes:  incomplete dominance.  With other genes, if you pair them with the same gene or one of lower dominance, that gene is expressed.  With the sable gene, a pair of them together has a different result than the sable paired with a color gene of lower dominance (e.g., "c_h" or "c").  Two sable genes produce a dark sepia color that is almost black, called "seal."  These seal-colored rabbits are "c_chl-c_chl."

 

The sable gene removes yellow from hair shafts and removes some of the darker pigments, giving a Holland Lop a shaded look (again, this shaded look is different from the shaded look caused by ee genes).  Leaving seal rabbits to their own color family, sable rabbits are either "c_chl-c_h" or "c_chl-c."

 

The Himalayan Gene -- Himalayan rabbits have even more of the color restricted so that only the muzzle, ears and feet (the points) show the rabbit's color.  The rest of the fur is pure white.  Thus, Himalayans are also called "pointed whites."  Himalayans come in just two geneotypes:  "c_h-c_h" and "c_h-c."

 

The Ruby-Eyed White Gene -- Ruby-eyed whites (REWs) are (surprise!) white rabbits with ruby eyes.  There are 24 main varieties of REWs (not counting Es and Ej genes--or countless other modifiers) because two "cc" genes together negate whatever the other four genes are contributing to the rabbit's coat color.  All color is erased from the fur and eyes.  Ruby-eyed whites are not genetically related to blue-eyed whites at all.

 

 [A big thanks to Elizabeth Van Horn for providing the photo of Checkmate's Snow Flake.]

 

What Happens When You Breed

 

Just like with other genes, if you breed two true-breeding color gene rabbits together, you will have offspring of the same.  That is, two true-breeding full color ("C-C") rabbits will produce all "C-C" offspring.  Two true-breeding chinchilla rabbits ("c_chd-c_chd") will produce chinchilla color family offspring.  Two seals will produce seals (they are always true-breeding).  Two true-breeding Himalayans will produce only Himalayans.  Two ruby-eyed whites will always produce ruby-eyed whites (they also are always true-breeding).  However, no true-breeding sable rabbit exists since a rabbit with two sable genes is a seal.  Rabbits who express the sable gene always carrying either a Himalayan gene ("c_h") or a REW gene ("c").

 

Of course the fun and uncertainty starts when you breed rabbits with different color genes together.  Let's take a look at a few different combinations.

 

Since we've already touched on the idea that there are no true-breeding sable rabbits, we'll look to see what happens when we breed two rabbits that are expressing the sable gene, such as two sable points.  We'll make one parent carry the Himalayan gene and the other the REW gene.  You will get approximately half sable rabbits, 1/4 seal rabbits and 1/4 Himalayans rabbits, on the average.  Look at the chart below to see how this works.

 

 

What happens when you breed a true-breeding full color rabbit (C-C) with a chinchilla color family rabbit that carries the sable gene (c_chd x c_chl)?  You will find that anytime you breed a true-breeding full color rabbit with any other rabbit, all of the offspring will be full color rabbits.  The offspring will carry the other parent's genes, however, and can be expressed in future generations.  Let's look at the results of the "CC" x "c_chd-c_chl" rabbits.

 

 

You may wonder whether you can get a sable, chinchilla, Himalayan or REW from breeding two full color rabbits, such as two black tortoiseshells.  The answer is definitely, "Yes."  Remember that the other color genes can "hide" under the more dominant full color gene.  By looking over a rabbit's pedigree you can get an idea of what could be lurking, but that doesn't preclude a surprise.  Ancestor rabbits may have other-color-gene siblings that you can't see on your rabbit's pedigree.  If you had the whole family tree, it might make more sense. 

 

In any case, let's see what happens when we breed a full color rabbit that carries the REW ("c") gene with a full color rabbit that carries the sable gene (c_chl).  The resulting offspring are primarily full color rabbits, but a half of them carry the other color genes and 1/4 are sable gene color family rabbits.  Take a look at the table below to see how this happens.

 

 

Test Breeding for Color Genes with REWs

 

Sometimes we do get puzzling results from breeding rabbits.  Phenotypes (what you see) are sometimes easy to confuse.  But by using a REW, you can test the color genes of a particular rabbit.  Because the REW is definitely and obviously "c-c," all offspring will exhibit the color genes of the other parent (remember, since "c" is the least dominant, nothing can "hide" under it).  It does not matter whether the doe or buck is the REW, the process works the same way.  [Note: you cannot use a blue-eyed white in this way; blue-eyed whites have a totally different genetic make-up.]

 

Perhaps we have a rabbit that we think is either a broken seal or a broken black [Note:  solids can be distinguished from the fur on the bottom of their feet--blacks have gray around their footpads and seals have brownish sepia color around their footpads; brokens have white].  Approximately half of the offspring will have one of the color genes of the tested rabbit while the other half will have the other gene.  If even one of the resulting offspring shows a full color gene, the tested rabbit is black.  If all of the offspring are sable color family rabbits (and there are enough offspring to eliminate errors of chance), the rabbit is probably a seal.

 

Note that all offspring in this case carry the REW gene.  Breeding two of the resulting offspring together can produce more REWs.  The top chart shows a REW bred with a full color rabbit that carries the sable gene.  The second chart shows a REW bred with a seal.  Notice that both pairings can produce sable family color rabbits, but only the black can produce the full color rabbit.

 

 

 

 

Color Families

 

I use the term "color families" to describe groups of colors that vary by only one gene.  Every color belongs to a number of color families.  You can use your knowledge of color families to help you breed for specific colors (and to understand how colors are produced by certain breedings).  Since color family rabbits only vary by one gene, they are the next best thing to breeding two rabbits of the color you are attempting to produce.

 

Conclusion

 

The color gene is the most complicated of all genes that determine Holland Lop fur color.  The color gene controls where color will show and how much will show there.  There are five color genes that produce six color families:  full color, chinchilla, seal, sable, Himalayan and REW.  The genes range from full color over the entire body ("C") to no color ("c").  The sable gene is often thought of as a shading gene, but the ee gene can also produce a type of shading.

 

Less dominant/more recessive genes can hide under other color genes.  You can use REWs to test for color genes.  Knowing how colors are related to each other, that is, those that vary by only the color gene, can help you produce the colors you desire.