How do breeders use the A, E, and D series?

Breeders use the A, E, and D genetic series, along with modern DNA testing, to understand a dog’s hidden genotype and predict the coat colors and patterns of future litters.

Here is how breeders utilize each series:

• The A-Series (Agouti or ASIP gene): This series determines the underlying “base” color of the dog’s coat by controlling the switching between black pigment (eumelanin) and red/yellow pigment (phaeomelanin). The dominant A allele causes black pigment to appear throughout the coat, forming the basis for Black, Blue, Merle, and Harlequin Great Danes. The recessive ay allele creates a sable coat, which is the base color for Fawn and Brindle Danes. Breeders test the A-series to reveal hidden colors; for instance, a solid black dog might carry the recessive fawn gene, or a dog may carry specific alleles for “tan point” (at) or “wild sable” (aw) patterns.

• The E-Series (Extension or MC1R gene): While historically controversial, genetic research has clarified that the E-series is responsible for the black mask trait commonly desired on Fawn and Brindle Danes. The mask is a dominant trait (EM), but it can be hidden on solid black, blue, harlequin, or merle dogs because their dark coats or spotting patterns obscure it. Breeders use E-series DNA testing to determine if a dog is homozygous for the masking trait. For example, by testing a black-masked fawn, a breeder can confirm she carries two copies of the mask gene, guaranteeing she will pass a mask to all her puppies regardless of the sire chosen.

• The D-Series (Dilute or MLPH gene): This series determines whether a dog’s dark pigment will be diluted, turning black pigment to blue (grey) or brown pigment to lilac. The normal D allele produces full color, while the d allele causes dilution. Because dilution is recessive, a dog must inherit two copies of the d allele to have a visibly blue coat. Breeders use D-series testing to identify carriers (dogs with a D/d genotype) so they can plan matings strategically. This allows them to either intentionally produce blue puppies or avoid inadvertently diluting the coat, masks, or brindle stripes of their fawn and brindle lines.