The visible color in the shanks/feet of chickens is the result of a combination of colors in the upper skin and deeper skin. Shank/foot color basically is controlled by three genes, one of which is sex-linked and located on the Z sex chromosome. Table 1 shows the shank/foot colors that result from the major gene combinations. Remember that each chicken has two copies of each gene. The table is only a guide because other genes affect shank/foot color as well. For example, the sex-linked barring gene, B, is located on the Z sex chromosome and is a strong inhibitor of melanin pigment in the skin. Barred Plymouth Rock chickens would not have light shanks if not for the fact that they have the sex-linked barring gene. Female Barred Plymouth Rocks (having the sex chromosomes ZW) tend to have darker shanks than the males (having the sex chromosomes ZZ) due to the dose effect of the barring gene in the male.