Figure 1.

(a) The brown mackerel tabby constitutes the wild type cat. The brown fur is an optical illusion, being banded with black (eumelanin) and yellow pigment (pheomelanin). Wild type alleles of genes can be dominant or recessive and are designated with a superscript ‘+’. Alleles at the different color loci can be represented for the brown mackerel tabby as: A+ -, B+ -, C+ -, D+ -, E+ -, L+ -, o⁺o⁺, s⁺s⁺, T™ -, titi, ww+w*. (b) One variant in the locus Agouti, the non-agouti allele, a, can make the fur appear solid, although all the other alleles are the same. Only the pheomelanin is replaced with black pigment in the solid black cat, which still has tabby markings. The black cat can be represented as: aa, B+ -, C+ -, D+ -, E+ -, L+ -, o+o+, s+s+, T -, titi, w+w*. (c) This silver Oriental Shorthair kitten displays the effect of the Inhibitor gene that removes pheomelanin from the coat and the effect of the Ticked allele that epistatically suppresses Tabby markings: A+ -, B+-, C+ -, D+ -, E+ -, I -, L+ -, o+o+, s+s+,Ti^a -, w+w+- (Epistasis is a phenomenon whereby one gene locus masks or modifies the phenotype of a second gene locus)