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Phaeomelanin (red) dilution 1

The amount of phaeomelanin deposited in the coat determines the intensity of the red coloration. This is most noticeable in “ee” dogs which are devoid of any eumelanin or black/brown which can mask any red. This type of dilution is also present and visible in sable and other agouti patterns where fawn gets diluted to white. Homozygous “ee” dogs can range from deep red all the way down to white. This range is determined by modifiers which either increase or decrease the amount of red pigment compared to an average shade of red. A mutation has been identified which when present in two copies dilutes the amount of red all the way to white. This is an ancient mutation and is present in many breeds. Some people are referring to this as an I locus mutation, but we know that there is at least one more locus which also dilutes red pigment so for now it is simply red dilution # 1.

In Poodles examined in the original study, every white Poodle (8 out of 67) had two copies of the mutation. Of the remaining 59 apricot/cream/red dogs there were two that had two copies of the mutation and were not white. This indicates the action of a second gene involved red pigment intensity.

VetGen Test ID C267
Autosomal recessive: 2 copies usually white, 0 or 1 copy apricot to red

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