The melanocortin 1 receptor (MC1R) gene controls production of the pigments eumelanin (black) and phaeomelanin (red/yellow). Six known variants of this gene are responsible for producing markings and coat colors including melanistic mask, grizzle/domino, black, and shades of red/yellow.
The Agouti Signaling Protein (ASIP) gene interacts with the MC1R gene to control red (phaeomelanin) and black (eumelanin) pigment switching in dogs, affecting amount, type, and distribution of the two pigments.
White spotting patterns that occur in many dog breeds do not have a uniform genetic basis, and the genetics are complex. In piebald/parti/random white spotting, the extent of white pattern expression varies, and markings are often asymmetrical.