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

An investigation was conducted among the progeny from crosses between Gold-Pencilled Hamburgh and Partridge Wyandotte bantams into the relationship between two plumage pattern phenotypes, pencilling and autosomal barring, both of which are arrangements of eumelanin expressed on a background of phaeomelanic pigmentation. A eumelanin restricting gene Db had previously 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 pencilling gene Pg. The F2 generation consisted entirely of three phenotypes: barred, pencilled and intermediary, with presumed genotypes DB/Db, db+/db+ and Db/db+ respectively, indicating that Ab and Pg are one and the same gene, for which I propose the retention of the symbol Pg. The gene action of Db when homozygous is therefore to prevent curvature, so changing pencilling into barring.