Its expression is dependent upon the animal not possessing Em nor E nor being homozygous for e. eh is theorized to be on the E locus and to have no effect on ky/ky dogs. All cocker spaniels are homozygous for at, so it is unknown how the gene may function in the presence of other A-series alleles. K (dominant black) locus The alleles at the K locus (the β-Defensin 103 gene or DEFB103) determine the coloring pattern of an animal's coat. There are three known alleles that occur at the K locus: KB = Dominant black (black) kbr = Brindle (black stripes added to tan areas) ky = Phaeomelanin permitted (pattern expressed as per alleles present at A and E loci) The dominance hierarchy for the K locus alleles appears to be as follows: KB > kbr > ky. KB causes a solid eumelanin coat (black, brown, grey or taupe) except when combined with e/e (tan or white), Eh/- (Cocker sable) or Em/- G/- and appropriate coat type (light eumelanin with dark eumelanin mask) kbr causes the addition of eumelanin stripes to all tan areas of a dog except when combined with e/e (no effect) or EG/- atat non-KB/- (eumelanin and sabled areas become striped, tan areas remain tan) ky is wild-type allowing full expression of other genes. Interactions of some genes with brindle Alleles at the Agouti (A), Extension (E) and Black (K) loci determine the presence or absence of brindle and its location: Patches and white spotting The Merle (M), Harlequin (H), and Spotting (S) loci contribute to patching, spotting, and white markings. Alleles present at the Merle (M) and Harlequin (H) loci cause patchy reduction of melanin to half (merle), zero (harlequin) or both (double merle). Alleles present at the Spotting (S), Ticking (T) and Flecking (F) loci determine white markings. H (harlequin) locus DNA studies have isolated a missense mutation in the 20S proteasome β2 subunit at the H locus. The H locus is a modifier locus (of the M locus) and the alleles at the H locus will determine if an animal expresses a harlequin vs merle pattern. There are two alleles that occur at the H locus: H = Harlequin (if M/-, patches of full colour and white) h = Non-harlequin (if M/-, normal expression of merle) H/h heterozygotes are harlequin and h/h homozygotes are non-harlequin. Breeding data suggests that homozygous H/H is embryonic