Testing Summary
The I Locus (Intensity) coat color test evaluates the MFSD12 gene to determine the I locus genotype for the dog. This Mutation has been associated with the extreme dilution of the light, yellow to red pigment (i.e., phaeomelanin) in many breeds, associated with an e/e genotype at the E locus. The phaeomelanin pigment can also be seen in dogs with a dark coat color that express their A locus (Agouti) genotype; for example, a dog with tan (phaeomelanin) points (ky/ky and at/at) or the light base color of hairs on sable/fawn (ky/ky and Ay/-) dogs.
Dogs with I/I and I/i genotypes typically have an unmodified (yellow to red) phaeomelanin pigment. Dogs with an i/i genotype typically have a less intense, cream or white phaeomelanin pigment. However, there are other, unknown genes that influence the final shade of phaeomelanin; genes responsible for the red shade of phaeomelanin are still unknown. Dogs that carry at least one copy of the i Allele can produce light cream or white dogs if bred to another dog that is also light cream or white (i/i) or a Carrier of light cream or white (I/i). The color of the dog’s nose and footpads is still dependent on the B locus; there is no evidence that the I Locus impacts the nose and footpad color.
The I Locus (Intensity) coat color test reliably determines if a dog has one of the following genotypes at the I locus:
I/I | This dog does not carry a copy of the i mutation and has an I locus genotype of I/I which does not result in the lightening of the light, phaeomelanin pigments that produce the dog’s coat color in an e/e dog. This dog will pass one copy of I to 100% of its offspring and cannot produce i/i dogs. Interpretation: Normal Intensity |
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I/i | This dog carries one copy of the i mutation and has an I locus genotype of I/i which does not result in the lightening of the light, phaeomelanin pigments that produce the dog’s coat color in an e/e dog. This dog will pass one copy of I to 50% of its offspring and one copy of i to 50% of its offspring. This dog can produce i/i offspring if bred to a dog that is also a carrier of an i mutation (I/i or i/i). Interpretation: Normal Intensity (carrier) |
i/i | This dog carries two copies of the i mutation and has an I locus genotype of i/i which results in the extreme lightening of the light, phaeomelanin pigments that produce the dog’s coat color in e/e dogs. This dog will pass one copy of i to 100% of its offspring. This dog can produce i/i offspring if bred to a dog that is also a carrier of an i mutation (I/i or i/i). Interpretation: Reduced intensity, likely light shades or white |