Duplex Comb

The Duplex Comb gene causes chickens to split their comb in half, giving the appearance of two separate combs. On the wildtype single comb, the duplex comb gene creates the typical "v-comb", or two prongs that form an overall "v" (2). This can vary in size, with some being large and overgrown, and others being small and set close to the head (1).Typically, the front part of the comb stays attached, while the back branches off. On the pea comb, the duplex comb creates a much more uneven look, with two longer sides and a middle part to the comb. With a rose comb, the comb branches apart towards the end, but has many uneven bumps and tines across the surface.

It is completely separate from the buttercup comb gene, though they are on the same locus (8). That means a chicken can only be homozygous for the v-comb or buttercup comb, but not both. The v-comb is also linked to the polydactyly and multiple spur genes (4), meaning that a bird is more likely to inherit five toes if it also presents the duplex gene. It is not uncommon for the two to be separate, however.

The APA recognizes the Crevecoeur, La Fleche, Houdan, Polish, and Sultan to have the duplex comb gene. (7) Other breeds that naturally have the gene include the Appenzeller Spitzhauben and the Dutch Owlbeard.

Breeding with Duplex Comb:

V-comb x V-comb = 100% V-comb (V/V x V/V = 100% V)

V-Comb x Single Comb = 100% Het. V-Comb (V/V x v+/v+ = 100% V/v+)

V-Comb x Het. V-Comb = 50% V-Comb, 50% Het. V-Comb (V/V x V/v+ = 50% V/V, 50% V/v+)

Het. V-Comb x Het. V-Comb = 25% V-Comb, 50% Het. V-Comb, 25% Single Comb

(V/v+ x V/v+ = 25% V/V, 50% V/v+, 25% v+/v+)

Het. V-Comb x Single Comb= 50% Het. V-Comb, 50% Single Comb(V/v+ x v+/v+ = 50% V/v+, 50% v+/v+)