The colour patterns in blue merle can be black, blue, or liver. The nose is often black, but it can also be liver-colored.
Genes
Merle coats are found in merle dogs and some other breeds with merle coats. The M locus causes the coloration pattern because it alters the protein that controls the nuclei in melanocytes (the cells that produce pigment). This protein is called tyrosinase-related protein (TRP), and it controls how melanocytes develop pigmentation during development in an embryo or fetus.
It is a dominant trait, which means a dog can only be homozygous for the M allele and have merle coloring. There are different types of merle dogs, red merle, double merle, and blue merle. Merle dogs usually have one white coat and one red coat but can also have both tails with different colors (i.e., black and tan). The merle gene is carried on the X chromosome; therefore, dogs who are carriers of this mutation will not be affected by merling unless they also have one copy of the merle gene from each parent. The M locus is a genetic mutation that causes a change in the coat color of dogs.
Table
