Isabella French Bulldogs | Testable Chocolate, Rojo, New Shade, Beautiful Chocolatey Goodness

By: Danielle Harris

* This post contains affiliate links, and we will be compensated if you buy after clicking on our links.

Masterpiece, Rojo - Spalding Farm Bullies
Isabella French Bulldogs
Masterpiece, Rojo – Spalding Farm Bullies

B Locus – Testable Chocolate

The other chocolate, known as Testable Chocolate, is found on the B locus.

B locus is actually responsible for dominant black. However, when 2 copies of “b” are passed on, the dog will then express a chocolate or liver coat. “b/b” is actually a mutation, like blue dilution (d).

In the dominant form of the B Locus, tyrosinase-related protein 1 is produced. This protein produces a pigment called eumelanin. Enough eumelanin is produced so that the dog’s coat appears black instead of chocolate. This dominant form appears when the dog has the “B” allele vs “b”.

A mutation in the gene can occur, causing a change in the production of the eumelanin.

This dilutes the black color pigment into a brown color. This mutated gene is known as the “b” allele or Testable Chocolate.

Rojo and New Shade Rojo French Bulldogs

When a dog has two copies of the recessive allele “b/b”, all black pigment appears brown, also referred to as liver or chocolate.

The dog must have b/b in order to have the brown coloration.


b/b- Rojo.

b/b co/co – New Shade Rojo or Double Chocolate

Isabella French Bulldogs

Isabella is not a single color on its own, It’s a color coat combination.

When talking about dna, it is incorrect to say a dog carries Isabella when referring to “b”. We just say carrying “testable chocolate”.

Isabella French Bulldogs require the dna of:

d/d, b/b

d/d, b/b, co/co – New Shade Isabella

Some People say Isabella French bulldogs are lilac but lilac french bulldogs are traditionally d/d, co/co.

Don’t forget to subscribe for updates and newsletters and follow on social!

Photo of author


French Bulldog
Find Everything You Need on Chewy!

Leave a Comment