Chapter 23 : An Adventure in Dog Hair, Part I

Abstract:

This chapter talks about an adventure in dog hair color. It uses the scientific terminology to describe the pigments and the cells that produce them. Pigmentation in dogs and other mammals is caused by the relative amounts and types of two classes of pigment: eumelanin and phaeomelanin. The eumelanins are the black and brown pigments, while the phaeomelanins are red and yellow. Both eumelanins and phaeomelanins are synthesized in pigment-producing cells called melanocytes. A schematic of the synthesis pathways is shown in the chapter. First, the enzyme tyrosinase converts the amino acid tyrosine into a chemical called dopa-quinone. The enzyme called tyrosinase-related protein 2 (TYRP2) is present, it converts the dopaquinone into a version of eumelanin that has a brown color—Cocoa’s pigment. If the enzyme called tyrosinase-related protein 1 (TYRP1) is present, it converts the brown version of eumelanin into the final, black-colored pigment. It talks about two useful terms: genotype and phenotype.