How has DNA testing changed the Great Dane color standards?

DNA testing has provided definitive answers about the recessive genes dogs carry, fundamentally changing how Great Dane breeders approach coat color and breeding standards. This technology has shifted the Great Dane community away from pedigree-based guesswork and led to several major changes in breed standards:

Acceptance of the Merle Coat. For over a century, the merle coat was a disqualifying color in the Great Dane breed. However, DNA testing definitively proved that the harlequin pattern is actually a dominant modifier of the merle gene. This means the merle gene is absolutely essential to creating the harlequin pattern, and it is impossible to breed harlequins without a high probability of producing merle offspring. Recognizing this biological reality, breeders successfully petitioned the Great Dane Club of America (GDCA) to accept the color. As of January 1, 2019, merle Great Danes became officially recognized and eligible to compete in American Kennel Club (AKC) conformation shows.

Revision of the GDCA “Color Code”: Historically, the GDCA maintained a strict Color Code that allowed breeding only within specific color families (e.g., fawn/brindle, black/blue, and harlequin/black). This was done to avoid producing disqualified color and pattern combinations. The old code relied on ensuring dogs were clear of certain colors for four generations to lessen the chance they carried unapproved recessive traits. Because DNA testing now provides a clear understanding of the exact genes a dog carries, the GDCA has been extensively revising its Color Code. Today, breeders can use DNA testing to determine if a black dog carries a recessive blue or fawn gene, allowing them to confidently plan litters that avoid non-recognized colors while safely expanding the gene pool.

Preventing “Double Merle” Health Defects. Before DNA testing fully mapped the harlequin and merle genes, the original Color Code permitted Harlequin-to-Harlequin matings. However, DNA research revealed that because all harlequins carry the merle allele, breeding two harlequins is genetically a merle-to-merle mating. This specific combination results in a 25% chance of producing “double merles” (dogs homozygous for the merle gene). Double merles suffer from a high incidence of congenital deafness and visual defects, such as abnormally small eyes (microphthalmia). The new DNA-informed guidelines help educate breeders on how to avoid these specific pairings, prioritizing the health of the puppies alongside their coat color.