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Extension (Coat colour E-Locus Dog)

The base colour of the dog is determined by the interaction of the the E locus (Extension), A locus (Agouti) and the K locus (BlacK). The alleles of these loci determine if and where the pigment eumelanin (black colour) and the pigment phaeomelanin (red colour) can be produced and how these two are distributed over the body.

 

The E locus has different alleles which determine whether and where the dark pigment eumelanin can be produced. If eumelanin cannot be produced, the dogs show a light sometimes reddish colouring, because only the red/light pigment phaeomelanin is produced.

General Information

The E locus has different alleles which determine whether and where the dark pigment eumelanin can be produced.

 

  1. The Em allele is inherited dominantly and codes for the "melanistic mask" pattern.
  2. The Eg allele is inherited dominantly and codes for the markings "Grizzle/Domino" in Salukis and Afghan Hounds.
  3. The E allele is inherited dominantly and codes for a dark coat colour (wild type). The black pigment can be produced all over the body.
  4. The e-allele is inherited recessively and codes for a light base colour (red/cream/yellow).

 

  • In the allele combination e/e only the pigment phaeomelanin (red/light colour) is produced.
  • The Em allele for melanistic mask is dominant over the Eg allele for grizzle/domino. The black mask thus masks the grizzle/domino colouration.

 

Impact of/on other Loci:

 

A-locus:

  • The pigment eumelanin (black colour) must be produced (at least one copy E, Em or Eg) for the expression of the alleles of the A locus to be visible in the phenotype.
  • In recessive black dogs (a/a) the mask and the grizzle/domino colouration is not visible in the phenotype, but they can carry black mask in the genotype and pass it on to offspring.
  • For the grizzle/domino colouration (light mask) to be visible in the phenotype, the allele combination at/at must be present.
  • The black mask is particularly well seen in dogs with the colour Fawn/Sable (Ay/?).


K-locus:

  • The pigment eumelanin (black colour) must be produced (at least one copy E, Em or Eg) for the expressions of the alleles of the K locus to be visible in the phenotype.
  • In dominant black dogs (KB/KB, KB/ky) the melanistic mask and the grizzle/domino colouration is not visible in the phenotype, but they may carry melanistic mask in the genotype and pass it on to offspring.

 

B-locus:

  • The pigment eumelanin (at least one copy E, Em or Eg) can be diluted to the colour "Brown" by the b-allele of the B-locus. Animals with a light base colour (e/e) can be carriers for the b alleles. Here the diluton is only visible on the lighter skin of nose and lips.

Genotype and Lab Report

Inheritance: autosomal-dominant

 

  • Animals with one or two copies of the gene (Em/Em, Em/E, Em/e) show the phenotype „melanistic mask“.
  • Animals with one or two copies of the gene(Eg/Eg, Eg/E, Eg/e) show the phenotypeGrizzle/Domino“.
  • Animals with one or two copies of the gene (E/E, E/e) show a dark coat colour (Wildtype).
  • Animals with no copy of the gene (e/e) show a light base colour (red/cream/yellow).

 

Genotypes

 

Em/Em = Two copies Em

Eumelanin is produced, the colour pattern Melanistic Mask is expressed and will be passed on to the offspring with a probability of 100%.

 

Em/E = One copy Em and one copy E

Eumelanin is produced, the colour pattern Melanistic Mask is expressed and will be passed on to the offspring with a probability of 50%. The hidden E allele is also passed on at 50%.

 

Em/e = One copy Em and one copy e

Eumelanin is produced, the colour pattern Melanistic Mask is expressed and will be passed on to the offspring with a probability of 50%. The hidden e allele is also passed on at 50%.

 

Eg/Eg = Two copies Eg

Eumelanin is produced, the colour pattern Grizzle/Domino is expressed and will be passed on to the offspring with a probability of 100%.

 

Eg/E = One copy Eg and one copy E

Eumelanin is produced, the colour pattern Grizzle/Domino is expressed and will be passed on to the offspring with a probability of 50%. The hidden E allele is also passed on at 50%.

 

Eg/e = One copy Eg and one copy e

Eumelanin is produced, the colour pattern Grizzle/Domino is expressed and will be passed on to the offspring with a probability of 50%.The hidden e allele is also passed on at 50%.

 

E/E = Two copies E

Eumelanin is produced, the show a dark coat colour and will pass it on to the offspring with a probability of 100%.

 

E/e = One copy E and one copy e

Eumelanin is produced, the dogs show a dark coat colour and will pass it on to the offspring with a probability of 50%. The hidden e allele is also passed on at 50%.

 

e/e = Two copies e

Only phaeomelanin is produced, the dog has a red/light coat colour.

Appearance

„Melanistic Mask“

The dog has black markings over the muzzle and face ("mask"). The mask is only visible if the rest of the coat colour is not black as well. Particularly good to see e.g. in dogs with the colour Fawn/Sable (A-Locus Ay/?).

 

Possible genotypes:

  • Em/Em
  • Em/E
  • Em/e

„Grizzle/Domino“

The dog has a light face mask with so-called "widow's peak". In Salukis this colouration is called grizzle and in Afghan Hounds domino. In order for the light mask to be visible in the phenotype, the allele combination at/at must be present at the A locus.

 

Possible genotypes:

  • Eg/Eg
  • Eg/E
  • Eg/e

Light base colour (yellow/red/cream/lemon)

The dog is yellow, reddish, sandy or cream coloured all over the body.

 

Possible genotypes:

e/e

Test Information

Locus Information: E-Locus

This test detects various changes in single base pairs in the MC1R geneGo to Shop

Literature

  • Everts, R.E., Rothuizen, J., van, Oost, B.A.: Identification of a premature stop codon in the melanocyte-stimulating hormone receptor gene (MC1R) in Labrador and Golden retrievers with yellow coat colour. Animal Genetics 31:194-199, 2000. Pubmed reference: 10895310
  • Newton, J.M., Wilkie, A.L., He, L., Jordan, S.A., Metallinos, D.L., Holmes, N.G., Jackson, I.J., Barsh, G.S.: Melanocortin 1 receptor variation in the domestic dog Mammalian Genome 11:24-30, 2000. Pubmed reference: 10602988.
  • Schmutz, SM., Berryere, TG., Ellinwood, NM., Kerns, JA., Barsh, GS.: MC1R studies in dogs with melanistic mask or brindle patterns. J Hered 94:69-73, 2003. Pubmed reference: 12692165
  • Dreger, DL., Schmutz, SM.: A new mutation in MC1R explains a coat color phenotype in 2 „Old“ breeds: Saluki and Afghan Hound. J Hered: 2010. Pubmed reference: 20525767. DOI: 10.1093/jhered/esq061
  • Further information is available at Online Mendelian Inheritance in Animals.
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