CHOCOLATE DNA OVERVIEW

Brown aka Chocolate

BB, Bb, bb

TYRP1 Gene. There are two alleles 1. B dominant full base color 2. b  recessive brown

TYRP1 is a modifier of eumelanin, not a dilution gene as in blue (dd). The dilution gene affects how dense the pigment is, which makes it appear pale as if you mixed white into black paint making gray. The chocolate bb does not dilute, but changes the shape of the molecules of the pigment. The different shape reflects light in a different way and therefore changes the black to chocolate.

When you have a bb dog, black pigment is modified to chocolate. If your dog is red or yellow base, the bb does not modify the hair color, but does modify nose, eyerims, and foot pads from black to chocolate and eye color to amber or gold.

RESULTS (UCDavis)

BB: Does not carry chocolate, full base color, cannot have chocolate offspring

Bb: Dog is base color and carries 1 copy of chocolate

bb: 2 copies of chocolate, full chocolate

DETAILS

The hair color on Chocolates can vary slightly, but, there is no getting around the LIVER Colored nose. The nose, eyeliner, and pads should be some variation of brown, whether Hershey type chocolate or a more diluted chocolate as in chocolate fawn/sable. If the nose is not liver (brown) it is not a true chocolate. Chocolate color in dogs is basically a modified Black dog, where black is modified to chocolate. For the Chocolate Gene to make a dark chocolate dog, the Full Black base has to be there.

The chocolate gene affects black pigment only. If a dog is bb, all of the black in the coat will be turned to chocolate. This includes all patterns. Chocolate turns the nose and eye color, usually to an amber, yellow, or gold color. The nose color is the best way to tell chocolate from a black or blue. When you combine a chocolate dog with a blue dog, bb + dd, you get a lilac, which is the color of a Weimaraner.

Chocolate is recessive, so it takes 2 copies to present on the dog. If a dog is full black base and is bb, all the black in its coat will become a chocolate. Bb and BB have no visible effect.

As if this were not confusing enough, I have now been advised that there are 3 Sequences to the b genotype. There are a number of different versions of the b allele, but all of them result in the same coat color. These variations mean you can have either b, b2, or b3 on your dog’s DNA. This can be on one or both sides of the complete gene.

Therefore, it is possible to have your dog dna any one of the following types:

Bb    Bb2    Bb3    bb    bb2    bb3    b2b    b2b2    b2b3    b3b    b3b2    b3b3

Some labs recognize all 3 sequences and some don't, so you could have a b2 or b3 on your dog and not know it.

TESTABLE VS NON TESTABLE CHOCOLATE

Testable: bb

Non-Testable: bnbn

To hold down confusion when posting DNA for the Non-testable Chocolate, Rare Bulldogs encourages breeders to post Non-testable Chocolate as: bn/bn (n of course referring to Non-testable), and Testable Chocolate as it has always been: bb.

Science is science and cannot be denied. This page will include experienced opinions from breeders and scientific fact from Genetic tests and input from Geneticists and Doctors of Veterinary Medicine, professionals in the field.

The French Bulldog and Chocolate Color

Our main topic here is testable and non-testable chocolate color in French Bulldogs. For the purposes of this article, we will use the term “Normal Chocolate” for the testable, and “Mutated Chocolate” for the non-testable. The Normal Chocolate is the same test that has always been around for chocolate (brown) for years and is used in many breeds. The Mutated chocolate is actually more common in FB, but the gene/mutation/modifier has yet to be found.

For many years there have been visually chocolate FB’s that have tested BB…non chocolate, so there ARE chocolate FB’s that definitely have chocolate hair and a chocolate nose that test BB. This Mutated Chocolate Gene or Modifier for this type chocolate has yet to be discovered and therefore no test is available at this time for those dogs. Recently, we have quite a few FB lines that do test Bb or bb, and the dogs in those lines that test bb actually look Chocolate.

A lot of people/breeders claim that these lines are mixed with other breeds to have brought the testable b in, even though these dogs are visibly chocolate, which is ironic since these same ones claim they have chocolate FB’s that test BB and also do not look chocolate but rather, black, faded black, or seal with a bronze or other color undertone. Not one of these ones can produce any proof that the testable lines are mixed, while at the same time, many of these Bb or bb dogs have been parentage DNA tested and have been found to be 100% FB. Therefore this claim of mix breeding is 100% unsubstantiated.

From the Geneticist: "The French Bulldog has two ways to be chocolate. One we can test for, but has been historically rare in the FB, and one that is still unknown, and seems to be the most common way the FB are chocolate. Recently, we are seeing more FB show up with the testable chocolate."

Lilac Bulldogs start out black, then diluted, not once but twice by the chocolate gene, then the blue gene. The [bb] allele dilutes the black to brown, and [dd] dilutes the black to blue. Try mixing blue and brown paint, you will get some shade of Purple or Lilac. The Lilac should be shiny and look weimaraner gray (or some shade of purple or lilac) against black objects or in the sun unless it is the Seal Color. The nose, eyeliner, & pads are some shade of purple.

In the case of the Lilac Fawn, although the HAIR is not diluted by the [bb,dd] genes, the pigment in the nose, foot pads, and eyeliner is diluted to purple which can vary in shade.