Harlequin is a complex pigmentary trait of coat colour, characterized by a pattern of distinctive black patches on a white background. It is controlled by heterozygous mutations of merle locus and a modifier harlequin locus. The harlequin gene only influences the dog’s phenotype in combination with the merle gene. If a dog has a non-merle genotype (mm) the harlequin gene will not influence the dog's phenotype. Animals with HH genotype are not viable, as it causes lethality early in embryogenesis.
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MM
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Mm
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mm
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HH
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MM/HH
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Mm/HH
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mm/HH
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lethal
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lethal
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lethal
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Hh
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MM/Hh
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Mm/Hh
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mm/Hh
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white
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harlequin
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carrying harlequin
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hh
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MM/hh
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Mm/hh
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mm/hh
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double merle
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merle
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Non- merle/ Non-harlequin
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mm = non merle, Mm = merle, MM = double merle
hh = not harlequin, Hh = harlequin, HH = prenatal lethal
