How do breeders use A and E genes to find masks?

Breeders use the A and E genetic series in tandem with DNA testing to determine whether a dog carries the black mask trait and whether that mask will be visible in its offspring.

• The A-Series (Agouti gene): This locus determines the dog’s underlying base pattern. For a mask to be visually noticeable, the dog must inherit the specific alleles on the A-series that produce a lighter base coat, such as the sable/fawn alleles (a 

y

 ) responsible for Fawn and Brindle Danes.

• The E-Series (MC1R gene): This locus controls the actual presence of the mask, which is a dominant trait (E 

M

 ).

Because the mask is only visible on lighter coats, a dominant mask can be completely hidden on dogs with dark or heavily spotted coats, such as solid blacks, blues, merles, and harlequins. To “find” these hidden masks, breeders use DNA testing at the E locus to determine if a dark-colored dog secretly carries the mask gene.

Furthermore, breeders use E-locus testing on dogs that already display a visible mask (such as a black-masked fawn) to determine whether they are homozygous for the trait. If the test reveals the dog carries two copies of the mask gene, the breeder knows that the dog will pass the mask trait to 100% of its puppies, guaranteeing a mask on the offspring regardless of the sire chosen.