Merle factor

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Australian Shepherd with blue merle coloring

The so-called merle factor ( merle for short ) is one of the many different color variations of the fur in dogs and is particularly widespread in collie breeding. The basic color of the fur is lightened in places with Merles in such a way that irregular, torn-looking spots in the basic color can be seen on a lightened background.


The merle factor is due to the merle gene in the dog's genome . It is a mutation of the silver locus gene (Pmel17), which is found on chromosome CFA10 in domestic dogs .

The merle gene only brightens eumelanin , while it leaves areas of fur in which exclusively pheomelanin is found unchanged.

If a heterozygous carrier of the merle gene is paired with a dog that does not have the gene, statistically 50% merle and 50% different colored puppies are to be expected. In practice, usually under 50% are Merle puppies.


Effect of the merle gene on eu- and pheomelanin:
From left to right: 1. Black, red and white without the merle gene; 2. brown, red and white with the merle gene, 3. black, red and white with the merle gene, 4. brown, red and white without the merle gene.
The light brown (“red”) markings around the mouth and on the legs caused by Phäomelanin are not influenced by the merle gene, while the black or dark brown areas caused by eumelanin are irregularly lightened in the merle dogs. The pure white spots under the belly, the blaze on the face and the white feet are due to a different gene.

Eumelanin is what causes the black coat color. A mutation of the Braun locus results in incomplete oculocutaneous albinism type 3 ( OCA3 ). As a result, areas of the fur in which only eumelanin is produced are lightened to brown or gray (silver-gray).

The colors based on eumelanin like black and brown can be lightened by the merle gene. In the areas colored in this way or in individual black or brown hairs, white marks appear. They can appear as large spots or as fine speckles. Sometimes the black is also lightened to a gray, which can vary from a dark gray-blue to a pinkish tint to a delicate light gray. Correspondingly, the brown created by the brown locus can be lightened to lighter brown tones.

The eyes can be monochrome brown, monochrome blue, or mixed colors - there are dogs that have one blue and one brown eye as well as dogs that combine both colors in one eye.

The recessive " allele e" (English recessive yellow ) of the extension locus causes homozygous presence ("ee") that a dog only produces the yellow or reddish-brown-looking pheomelanin on the entire body and is therefore a solid red-brown to gold-colored. Since the merle gene cannot influence the pheomelanin, dogs with this brown coloration do not show the typical merle pattern anywhere on the body. In breeds with occurrence of merle, therefore, caution is advised with animals of this color, as otherwise one could unknowingly pair two carriers of the merle gene with each other. Areas of fur colored brown by pheomelanin in other fur drawings, such as the burn in dogs with red markings on the face and legs or the light hair in the fur of the flamed dogs, are also not lightened by the merle gene.

Health effects of the homozygous form

Great Dane, which is genetically hereditary for the merle gene and therefore has a malformation of the eyes.
Inheritance scheme of the strictly forbidden mating: M = Merle factor available m = Merle factor not available.
Female with merle gene and coat color genotype "ee" has puppies from a merle male. Some of the puppies will have severe deformities.

The merle gene is inherited as an intermediate . Dogs that have the gene only once, i.e. are heterozygous, are usually healthy. In addition to a greater proportion of white in the fur, the merle gene in some cases leads to malformations of the inner ear with deafness. In purebred ( homozygous ) animals, 10% are deaf on one side and 15% on both ears. Of the mixed breed animals, 2.7% are one-sided, 0.9% are completely deaf. Malformations of the eyes can also occur, especially in homozygous animals. Affected animals can lag behind littermates in development, show a reduced zest for life and sometimes die before sexual maturity.

Therefore, for reasons of animal welfare, the mating of two carriers of the Merle factor is not recommended. The targeted breeding with a genetic defect for purely aesthetic reasons is highly controversial. In the “Expert Opinion on the Interpretation of Section 11 of the Animal Welfare Act (Prohibition of Torture Breeding )” ( BMELV ), a general recommendation is made to refrain from breeding with the Merle gene. (Animal Welfare Act, Section 11, Paragraph 1: " It is forbidden to breed vertebrates if it is to be expected that in the offspring or their offspring, hereditary parts or organs are missing or unsuitable for species-appropriate use ... and thus pain, Suffering or harm occurs ".)


Merle comes from Great Danes and Dachshunds of the color "Tiger", Collies , Shelties and others with the color designation Blue Merle, Corgies , Foxhound Beats , Catahoula Leopard Dog , Dunker dogs , some herding dog beats such as Mudi , Bergamasker Shepherd Dog , Border Collies , Bobtails , Australian Shepherds and colors of the old German herding dog , the Beauceron , the Chihuahua , the Prague Ratter and the Jack Russell Terrier before as well as other breeds of other breeds not recognized by the FCI .

See also


  • D. Dausch, W. Wegner, W. Michaelis, I. Reetz: Eye changes in the dog's Merle syndrome . In: Graefe's Archive for Clinical and Experimental Ophthalmology . tape 206 , no. 2 , 1978, p. 135-150 , doi : 10.1007 / BF00414621 .
  • Rainer Brinks: Defective Merle Factor. On : 2001 ( [1] ).
  • Leigh Anne Clark, Jacquelyn M. Wahl, Christine A. Rees, Keith E. Murphy: Retrotransposon insertion in SILV is responsible for merle patterning of the domestic dog . In: Proceedings of the National Academy of Sciences . tape 103 , no. 5 , 2006, p. 1376-1381 , doi : 10.1073 / pnas.0510714103 . PMID 16407134 .
  • Federal Ministry of Food, Agriculture and Consumer Protection (BMELV): Expert opinion on the interpretation of Section 11 of the Animal Welfare Act (prohibition of torture breeding) .
  • B. Hédan, S. Corre, C. Hitte, S. Dréano, T. Vilboux, T. Derrien, B. Denis, F. Galibert, MD Galibert, C. Andre: Coat color in dogs: identification of the Merle locus in the Australian shepherd breed . In: BMC Veterinary Research . tape 2 , no. 1 , 2006, p. 9 , doi : 10.1186 / 1746-6148-2-9 . , PMID 16504149 .
  • GM Strain, LA Clark, JM Wahl, AE Turner, KE Murphy: Prevalence of deafness in dogs heterozygous or homozygous for the merle allele. In: J Vet Intern Med. 2009 Mar-Apr; 23 (2), pp. 282-286. Epub 2009 Feb 3rd PMID 19192156 .

Web links

Commons : Merle Factor  - album with pictures, videos and audio files

Individual evidence

  2. Jess Chappell: Dog Coat Color Genetics: Double Merle