Intensity (I Locus)

General Information: The I Locus (IN), identified by mutations in the MFSD12 gene, specifically modulates the intensity of pheomelanin, which is responsible for producing red and yellow pigments in a dog's coat. Unlike eumelanin, which dictates darker pigments like black and brown, pheomelanin creates lighter hues such as red, gold, and cream. Dogs with a mutation at the I Locus may exhibit a range of diluted pheomelanin colors from deep gold to pale cream, depending on their specific genetic makeup and the interaction with other color genes. This mutation does not affect the eumelanin-based colors like black or brown, so dogs with both pheomelanin and eumelanin in their coats will only show dilution in the red or yellow areas, leaving black and brown areas unaffected.

Gene / Testing Information: Genetic testing for the I Locus (IN) involves analyzing the MFSD12 gene to detect the presence of the dilution mutation affecting pheomelanin. This mutation is inherited in an autosomal recessive fashion, meaning that a dog needs two copies of the mutated gene (i/i) to express the diluted coat colors. Carriers of the mutation (I/i) will not show the diluted coat color but can pass the mutation to their offspring. Breeding decisions should consider these genetic results to predict the coat colors of puppies, particularly if aiming for or avoiding specific color traits in breeds where coat color can impact desirability and value. Testing is crucial for breeders who wish to manage or utilize the expression of coat color intensity in their breeding programs, ensuring that matings are strategically planned to produce the desired coat color outcomes while maintaining genetic diversity and health within the breed.