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Agouti (Coat colour A-Locus Dog)

The base colour of the dog is determined by the interaction of the A locus (Agouti), the E locus (Extension) 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 A locus has several alleles that control the ratio of black to red pigment in the melanocytes (pigment-producing cells) and thus change the distribution of black pigment over the body.

    General Information

    The single genes are in a dominance order. If a higher-ranking (more dominant) allele is present, it also covers existing lower-ranking alleles. Depending on the combination of alleles present, different phenotypes of the dog can occur.

     

    1. The Ay allele is inherited dominantly, stands above the others and codes for Fawn/Sable.
    2. The aw allele is inherited recessively and codes for the Wild Colour ("wolf colour").
    3. The at allele is inherited recessively and codes for the "Black-and-Tan".
    4. The a allele is inherited recessively and codes for Recessive Black.

     

    Effects of/on other loci:

     

    • E locus: The pigment eumelanin (black colour) must be produced (E/E or E/e) for the expressions of the alleles of the A locus to be visible in the phenotype. Dogs with the light base colour (e/e) can be carriers for the A alleles, but these are not visible in the phenotype.
    • K locus: The expression of the alleles of the A-locus are only visible in the phenotype if the dog is not dominant black (ky/ky). The colour dominant black (K/K, K/ky) hides all A alleles expressions, these dogs can be carriers of the A alleles.

    Genotype and Lab Report

    Inheritance: autosomal-recessive

     

    Inheritance follows the order of dominance for the gene.

    • Animals with one or two copies of the gene (AY/a, AY/AY) show the fawn/sable phenotype.
    • Animals with one or two copies of the gene (aw/a, aw/aw) show the phenotype wild colour ("wolf colour").
    • Animals with one or two copies of the gene (at/a, at/at) show the phenotype "Tan pattern/Black marks".
    • Animals with no copy of the gene (a/a) are Recessive Black.

     

    Genotypes

     

    Ay/Ay = Two copies Ay

    The colour Fawn/Sable is expressed and will be passed on to the offspring with a probability of 100%.

     

    Ay/aw = One copy Ay and one copy aw

    The colour Fawn/Sable is expressed and will be passed on to the offspring with a probability of 50%. The hidden aw allele is also passed on at 50%.

     

    Ay/at = One copy Ay and one copy at

    The colour Fawn/Sable is expressed and will be passed on to the offspring with a probability of 50%. The hidden at allele is also passed on at 50%.

     

    Ay/a = One copy Ay and one copy a

    The colour Fawn/Sable is expressed and will be passed on to the offspring with a probability of 50%. The hidden a allele is also passed on at 50%.

     

    aw/aw = Two copies aw

    The colour wild colour ("wolf colour") is expressed and will be passed on to the offspring with a probability of 100%.

     

    aw/at = One copy aw and one copy at

    The colour wild colour ("wolf colour") is expressed and will be passed on to the offspring with a probability of 50%. The hidden at allele is also passed on at 50%.

     

    aw/a = One copy aw and one copy a

    The colour wild colour ("wolf colour") is expressed and will be passed on to the offspring with a probability of 50%. The hidden a allele is also passed on at 50%.

     

    at/at = Two copies aw

    The colour Black-and-Tan is expressed and will be passed on to the offspring with a probability of 100%.

     

    at/a = One copy at and one copy a

    The colour Black-and-Tan is expressed and will be passed on to the offspring with a probability of 50%. The hidden a allele is also passed on at 50%.

     

    a/a = Two copies aa

    The colour Recessive Black is expressed and will be passed on to the offspring with a probability of 100%.

    Appearance

    Fawn/Sable


    The dog is sand coloured or light brown with black hair tips all over the body. The hairs are bicoloured, but this is only visible in a longer coat.

     

    Possible genotypes:

    • Ay/Ay
    • Ay/aw
    • Ay/at
    • Ay/a

    Wild colour ("wolf colour")

     

    The dog shows the typical "wolf-grey" colour all over the body. The hair is banded, i.e. multicoloured with alternating light and dark parts.

     

    Possible genotypes:

    • aw/aw
    • aw/at
    • aw/a

    "Black-and-Tan"

     

    The dog is dark coloured on the body and has light brown markings on the belly, chest and face (muzzle). Especially the "brows", two light brown marks above the eyes, are typical.

     

    Possible genotypes:

    • at/at
    • at/a

    Recessive black

     

    The dog is black all over the body, the hairs are not bicoloured (brown/black) as in the other agouti genes.

    Recessive black and dominant black do not differ phenotypically.

     

    Possible genotypes:

    • a/a

    Test Information

    Locus Information: A-Locus

     

    This test detects various changes in single base pairs in the ASIP Gen.

    Literature

    Kerns, JA., Newton, J., Berryere, TG., Rubin, EM., Cheng, JF., Schmutz, SM., Barsh, GS.: Characterization of the dog Agouti gene and a non agouti mutation in German Shepherd Dogs. Mamm Genome 15:798-808, 2004. Pubmed reference: 15520882. DOI: 10.1007/s00335-004-2377-1

     

    Berryere, TG., Kerns, JA., Barsh, GS., Schmutz, SM.: Association of an Agouti allele with fawn or sable coat color in domestic dogs. Mamm Genome 16:262-72, 2005. Pubmed reference: 15965787. DOI: 10.1007/s00335-004-2445-6

     

     

    Further information is available at Online Mendelian Inheritance in Animals.

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