Description: The gene for merle occurs in many dog breeds but is only recognized as an FCI standard in some breeds. The merle-allele is a SINE insertion in PMEL (SILV) gene, which can be of various lengths, due to its retrotransposomal origin. SINE element inserted into a gene influence gene expression, and disrupting its function.  A typical SINE element is composed of a body and a poly-A tail of a variable length. It has been revealed that it might be the extent of the poly-A tail, which plays the peculiar biological role, visually recognized as different qualities of the Merle coat pattern. It was revealed that the poly-A tail, is prone to replication errors, caused by a slippage within replication, leading to possible length differences of the resulting replicons. It has also been observed that SINE insertions of different lengths do exist. Shorter SINE was ascribed to the allele Mc (Cryptic Merle) which has no apparent effect on the dogs‘phenotype, while longer SINE insertions were found to be responsible for the individual Merle phenotypes.

Locus M only affects the black pigment eumelanin, so any black, liver, blue or isabella in the coat will blend. The red pigment phaeomelanin is not affected by merle. So red dogs (genotype e/e) that are genetically merle will appear normal and be hidden merle, only the eyes may be blue. They do not express merle but can produce merle offspring depending on the genotype of the partner. A similar case of hidden merle is in sable dogs (with at least one Ay allele), where only the tip of the coat can be fused with eumelanin production, and it is difficult to visually distinguish merle from non-merle.

The Merle pattern can be seen in various breeds, such as the Australian Shepherd Dog, Australian Koolie, Border Collie, Dachshund, French Bulldog, Louisiana Catahoula, Labradoodle, Miniature American Shepherd, Miniature Australian Shepherd, Pyrenean Shepherd, Rough Collie, Shetland Sheepdog, Welsh Sheepdog, Cardigan Welsh Corgi, Chihuahua, Great Dane etc. Dogs heterozygous for the M allele show a typical coat pattern, however, dogs homozygous for the M allele may also exhibit auditory and ophthalmologic impairments and abnormalities together with very pale or completely white coat phenotypes (Strain et al. 2009).

A dog can be a mosaic, i.e. can carry multiple types of merle alleles in its cells. Intergenerationally, the merle allele may shorten or expand. Crossing individuals with merle alleles is generally not recommended due to potential health risks.

SINE can have negative health consequences, which have been observed rather frequently–vision and hearing impairment of the affected animals. In line with it, SINE insertions with a long poly-A tail, such as M or Mh may pose a greater risk of auditory or ophthalmic irregularities. It has been widely accepted that the most pronounced negative health consequences (both auditory and ophthalmic) relate to the M/M genotype (also called double merle). (All information is from research article Langevin et. al 2018).


Results according Langevin et al. written sizes of SINE insertion in base pairs (bp):

  • m: Wild type allele with no SINE insertion; coat is without Merle pattern
  • Mc: Cryptic Merle (200 to 230 bp); coat is without Merle pattern-solid coat
  • Mc+: Cryptic Merle (231 to 246 bp); coat is without Merle pattern-solid coat
  • Ma: Atypical Merle (247 to 254 bp); coat is without Merle pattern or is diluted-brownish hue
  • Ma+: Atypical Merle (255 to 264 bp); coat is not typical merle, merle is undefined, mostly diluted-brownish hue
  • M: Merle (265 to 268 bp); Classic Merle with randomly diluted areas alternating fully pigmented areas
  • Mh: Harlequin merle (269 and more bp); Minimal Merle, areas deleted to white, tweed

Here is a comparison between Murphy’s way of alleles description and that of Langevin et al.

The table can be downloaded in pdf here

Both types are available according to the customer’s choice.


Inheritance: incomplete dominant trait


Mutation: SINE insertion in PMEL (before SILV) gene with various length


Sample: EDTA whole blood (1.0 ml) or 2 buccal brushes. For official purposes, the confirmation of the dog’s identity by a Veterinarian is recommended.


The analysis is suitable for the following breeds: Australian Shepherd, Border Collie, Dachshund, Great Dane, Louisiana Leopard, Cardigan Welsh Corgi


Notes: Langevin M, Synkova H, Jancuskova T, Pekova S. Merle phenotypes in dogs – SILV SINE insertions from Mc to Mh. PLoS One. 2018 Sep 20;13(9):e0198536. doi: 10.1371/journal.pone.0198536. PMID: 30235206; PMCID: PMC6147463.