Dominant black and the K locus
Brindle lives at the K locus — the same locus that governs dominant black. The allele series runs like this:
How brindle looks
Brindling is stripes of eumelanin‑based colour laid over areas that are otherwise phaeomelanin (red) based. Because those stripes are eumelanin, they are modified by the B and D loci just like any other black‑based colour — so the stripes can be black, blue, chocolate or lilac depending on the dog.
The breeding rule
Brindle is dominant to its absence, so only one copy is needed to show it — and that leads to a hard rule of parentage.
At least one parent must be brindle
To produce a brindle pup, at least one parent must be brindle. If a brindle puppy appears in a litter with no brindle anywhere in the pedigree, then the sire recorded on the papers genetically cannot be the true sire. The one exception is a dog that is e/e or K, which can carry brindle without showing it.
