In the study done in 2010 of the Japanese gene, the researchers found the Harlequin and Tri-Colour Dutch weren't fixed on the A locus, and tested as AA, Aa and aa. 32 Harlequins and 8 Tri-colour Dutch were tested, and 7 of the Tri-Colour Dutch were homozygous for aa, with one Aa.
(Note that the...