The Harlequin gene causes a white background and the spots increase in size. Dogs that are not merle, cannot express the Harlequin colour/pattern. Breeding two dogs that both have a copy of the h locus “NH” is not recommended. A dog with two copies of Harlequin has not been observed and it is presumed to be lethal in utero. This gene is inherited as a dominant trait. Harlequin is a specific coat colour pattern marked by patches of full colour on a white background. This patterning is a result of the interaction of two different genes, the merle (M Locus) gene, PMEL, and a modifier gene, PSMB7, at the harlequin (H locus). Dogs who have one copy of H in addition to one copy of M will have the characteristic harlequin coat colour pattern. A dog with one copy of H but two copies of M (double merle) has a coat colour that can be indistinguishable from a dog without the harlequin variant. While the harlequin coat colour is not considered a defect, breeding studies indicate that inheriting two copies of the H gene variant is not compatible with life. Puppies with two copies of the PSMB7 gene variant (H/H) most likely die very early in gestation; therefore, breeding two dogs with harlequin coat colour (H/h) may result in reduced litter size.