lethal and that therefore all harlequins are H/h. The Harlequin allele is specific to Great Danes. Harlequin dogs (H/h M/m) have the same pattern of patches as merle (h/h M/m) dogs, but the patches are white and harlequin affects eumelanin and phaeomelanin equally. H has no effect on non-merle m/m dogs. M (merle) locus The alleles at the M locus (the silver locus protein homolog gene or SILV, aka premelanosome protein gene or PMEL) determine whether an animal expresses a merle pattern to its coat. There are two alleles that occur at the M locus: M = Merle (patches of full colour and reduced colour) m = Non-merle (normal expression) M and m show a relationship of both co-dominance and no dominance. On heterozygous M/m merles, black is reduced to silver on ~50% of the animal in semi-random patches with rough edges like torn paper. The fraction of the dog covered by merle patches is random such that some animals may be predominantly black and others predominantly silver. The merle gene is “faulty” with many merle animals having one odd patch of a third shade of grey, brown or tan. On homozygous M/M “double merles”, black is replaced with ~25% black, ~50% silver and ~25% white, again with random variation, such that some animals have more black or more white. Eumelanin (black/etc.) is significantly reduced by M/m, but phaeomelanin is barely affected such that there will be little to no evidence of the merle gene on any tan areas or on an e/e dog. However, the white patches caused by M/M affect both pigments equally, such that a fawn double merle would be, on average, ~75% tan and ~25% white. The merle gene also affects the skin, eye colour, eyesight and development of the eye and inner ear. Merle M/m puppies develop their skin pigmentation (nose, paws, belly) with speckled-edged progression, equally evident in e/e merles except when extensive white markings cause pink skin to remain in these areas. Blue and part-blue eyes are common. Both heterozygosity and homozygosity of the merle gene (i.e., M/m and M/M) are linked to a range of auditory and ophthalmologic abnormalities. Most M/m merles have normal-sized eyes and acceptably functional eyesight and hearing; most M/M double merles suffer from microphthalmia and/or partial to complete deafness. variation on merle allele There are other new discovery on M locus and it would be useful to add