Interpretation of your genetic coat color results.

Catherine Poissant
Apr 1
4 min read

A dog's coat color is determined by its DNA, more specifically by certain segments called loci, which influence coat pigmentation.

These loci are as follows:

E and B loci: Define the base color (Black, Brown, Red, Fawn…).
D locus: Responsible for color dilution (Blue, Beige, Cream, Isabella…).
K locus: Controls the brindle pattern and regulates the influence of the A locus.
A locus: Determines sable, agouti, and tan point patterns.
Em locus: Responsible for the presence of a facial mask.
S locus: Regulates white pattern distribution (Genetic test coming soon)
M locus: Responsible for the merle pattern.

It’s important to note that color names can vary from one breed to another.

Thus, the same genotype might be referred to differently depending on the breed, but genetically, it represents the same coat color.

E locus – Determination of Base Color

The E locus controls whether a dog expresses a fawn/yellow coat color or retains a different pigmentation regulated by the B locus.

There are two alleles at this locus:

e: Responsible for the fawn/yellow coat color.
E: Allows expression of the B locus.

Possible results:

e/e → The dog is fawn/yellow (e.g., Yellow Labrador, Lemon English Setter…).
E/e or E/E → The base color is determined by the B locus.

The E allele is dominant over e.

A dog with E/e or E/E will have a base color defined by the B locus.
A dog with e/e will necessarily be fawn/yellow and will only pass on the e allele to its offspring.

A puppy inherits one allele from each parent, which allows prediction of likely coat colors based on the parents’ genotypes.

B locus – Black or Brown Pigmentation

⚠️ The B locus only affects coat color if the dog has at least one copy of the E allele (E/E or E/e).If a dog is e/e, the B locus has no effect on coat color.

There are two alleles:

b: Produces brown pigmentation.
B: Produces black pigmentation.

Possible results (if the dog is E/E or E/e):

b/b → Brown dog (chocolate, liver…).
B/b → Black dog, carrier of brown (genetically, but not visibly).
B/B → Black dog.

The B allele is dominant over b, which means:

A dog with B/B or B/b will be black.
A dog with b/b will be brown and will only pass on the b allele to its offspring.

D locus – Color Dilution

The D locus affects the intensity of coat color, making it lighter or darker.

There are two alleles:

d: Responsible for color dilution.
D: No dilution.

Possible results:

d/d → Diluted color (Blue, Fawn, Cream, Isabella…).
D/d → Normal color, carrier of dilution.
D/D → Normal, non-diluted color.

If the dog is e/e (fawn/yellow):

d/d → Diluted fawn/yellow (e.g., Cream, Light Fawn).
D/d → Fawn/yellow, carrier of dilution.
D/D → Fawn/yellow, non-diluted.

If the dog is brown (E/E b/b or E/e b/b):

d/d → Fawned brown, often called Isabella or Beige.
D/d → Brown, carrier of dilution.
D/D → Brown, non-diluted.

If the dog is black (E/E B/B, E/e B/B, E/E B/b, or E/e B/b):

d/d → Blue (diluted black).
D/d → Black, carrier of dilution.
D/D → Black, non-diluted.

K locus – Brindle Pattern and Influence on the A Locus

This locus determines whether a dog will have a brindle pattern or whether the A locus will be expressed.

There are three alleles:

KB: Blocks the expression of the A locus.
kBr: Produces a brindle pattern while allowing the A locus to be expressed.
ky: Allows full expression of the A locus.

Possible results:

KB/KB, KB/kBr, or KB/ky → Blocks the A locus; the A locus has no impact on coat color.
kBr/kBr or kBr/ky → Brindle pattern.
ky/ky → Full expression of the A locus.