The H-locus in conjunction with the M-locus causes an unregular black and white pattern called... altro
Harlequin is a typical coat colour of Great Danes, which show black patterns on white background. This characteristic is caused by a modifier-gene for the M-locus. The dominant H-allele changes the Merle pattern to harlequin. Therefore, the genotype N/M at the M-locus is needed in addition to H/h. The dominant H-allele is lethal when found homozygous (H/H). Affected puppies die before birth.
3-5 days after arrival of the sample in the lab