Effect of the eumelanin restrictor Db on plumage pattern phenotypes of the domestic fowl

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Abstract
An investigation was conducted among the progeny from crosses between Gold-Pencilled Hamburgh and Partridge Wyandotte bantams into the relationship between 2 plumage pattern phenotypes, penicilling and autosomal barring, both of which were arrangements of eumelanin expressed on a background of pheomelanic pigmentation. A eumelanin restricting gene Db had been shown to be responsible for the barred phenotype when acting in conjunction with a pattern arranging gene Ab. The pencilled phenotype had been presumed to be caused by the presence of a penicilling gene Pg. The F2 generation consisted entirely of 3 phenotypes: barred, pencilled and intermediary, with presumed genotypes DB/Db, db+/db+ and Db/db+, respectively, indicating that Ab and Pg were the same gene, for which the retention of the symbol Pg was proposed. The gene action of Db when homozygous was to prevent curvature and changed penicilling into barring.