H-Locus (Harlequin)

Description

Harlequin is a coat pattern recognized only in Great Danes. The harlequin pattern is a result of a complex interaction between variances in the merle and the harlequin loci (M and H loci). The harlequin variant acts as a modifier of merle. All harlequin dogs must have one or two copies of the mutation responsible for the merle coloration pattern. Harlequin patterns cannot be expressed in dogs that are not merle or only have red pigment.

The dominant merle gene produces a coat consisting of dark spots on a diluted background. If a merle dog also inherits a single copy of the harlequin gene, the dark spots increase in size and the background pigment is eliminated.

Harlequin is presumed to be homozygous embryonic lethal. This means that if a dog inherits two copies of the H locus allele (H/H), the dog typically dies as an embryo and does not survive once born. No animals have been observed with 2 copies of the mutated gene. Therefore, all harlequin patterned dogs have only copy of the mutated gene (H/n). This means that all dogs are either n/n for harlequin (no harlequin pattern) or H/n (harlequin pattern)..

According to research conducted Dr. Leigh Anne Clark at Clemson University, over 59% of Harlequin-bred black or non-Merle dogs (including those with the mantle coloration) carry the harlequin mutation.