Merle is an incompletely dominant coat color pattern characterized by irregularly shaped patches of diluted pigment and solid color.
Phenotype: The merle pattern is characterized by irregularly shaped patches of diluted pigment and solid color.
Mode of Inheritance: Incomplete dominance
Alleles: N = Non-merle, M = Merle, Mc = Cryptic merle
Breeds appropriate for testing: Many breeds including American Bully, American Pit Bull Terrier, American Staffordshire Terrier, Australian Shepherd, Beauceron, Bergamasco, Border Collie, Cardigan Welsh Corgi, Catahoula Leopard Dog, Chihuahua, Cockapoo, Cocker Spaniel (American), Collie, Dachshund, Dunker, French Bulldog, Great Dane, Koolie, Mudi, Old English Sheepdog, Pomeranian, Pyrenean Shepherd, Shetland Sheepdog, Crossbred
Explanation of Results:
Dogs with N/N genotype are not expected to display a merle pattern. They cannot transmit these merle variants to any of their offspring.
Dogs with Mc/N or Mc/Mc genotype may display little to no merling ("cryptic merle") but possess a cryptic merle variant (Mc) that they may transmit to offspring.
Dogs with M/N or M/Mc genotype are expected to display a merle pattern if the dog also produces black pigment (that is, if dog is not e/e at MC1R). They may transmit a merle variant to their offspring. Breedings between two dogs that possess merle variants may produce "double merle" (M/M) offspring, which are prone to health problems (see below).
Dogs with M/M genotype are expected to display a merle pattern, likely appearing primarily white. These double merle dogs may have auditory, opthalmologic, skeletal, and other defects. They will transmit a merle variant to all of their offspring.
$45 one test per animal
$65 two tests for coat color/fur type/bobtail (same animal)
$85 three tests for coat color/fur type/bobtail (same animal)
+ $15 each additional test if ordering more than three coat color/fur type/bobtail tests on the same animal
Merle is an incompletely dominant coat color pattern characterized by irregularly shaped patches of diluted pigment and solid color. Breeds with merle include but are not limited to: Shetland Sheepdog, Collie, Border Collie, Australian Shepherd, Cardigan Welsh Corgi, Catahoula Leopard Dog, Dachshund, Great Dane, Bergamasco Sheepdog, and Pyrenean Shepherd.
Blue and partially blue eyes are typically seen with merle, and merle dogs often have a wide range of auditory and ophthalmologic defects. Dogs with two copies of merle (called double merle) are primarily white and can have multiple abnormalities of skeletal, cardiac, and reproductive systems, therefore breedings between two merle dogs are discouraged to avoid producing double merle offspring. Merle is governed by a SINE insertion in the Pmel17 or Silver (SILV) gene. In the horse, a mutation in this gene results in eumelanin pigment dilution and is also associated with eye abnormalities.
Merle only dilutes eumelanin (black) pigment; dogs with an MC1R e/e genotype (recessive red) have no black pigment and thus do not express merle but can produce merle offspring depending on the genotype of the mate. There are three alleles (variants) for merle: merle (M allele, SINE with longer poly-A tail), cryptic merle (Mc allele, SINE with shorter poly-A tail), and non-merle (N allele, no SINE insertion). Dogs with cryptic merle (also called phantom or ghost merle) typically display little to no merling and some may be misclassified as non-merles. Inheritance of merle is genetically unstable for both M and Mc alleles. During DNA replication and cell division, M may occasionally undergo poly-A tail reduction to produce Mc (germline rate of 3-4%) while Mc may undergo expansion and revert to M.
Because of the complexities of merle inheritance and potential health concerns, DNA testing is recommended to establish the genetic makeup of dogs for the merle gene for those breeds where this color dilution pattern is present.
1 copy of merle and 1 copy of cryptic merle are present.
1 copy of merle is present.
2 copies of cryptic merle are present.
1 copy of cryptic merle is present.
No copies of merle or cryptic merle are present.
Clark, L.A., Wahl, J.M., Rees, C.A., & Murphy, K.E. (2006). Retrotransposon insertion in SILV is responsible for merle patterning of the domestic dog. Proceedings of the National Academy of Sciences of the United States of America,103(5), 1376-1381. doi: 10.1073/pnas.0506940103