Table of Contents
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.
Dna:
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.
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