Research overview: the genetics of orange coat color in cats

The orange coloration of cats is governed by an X-linked locus, which is why most calico and tortoiseshell cats are female and display a patchwork of orange and black created by X-chromosome inactivation. This overview surveys the long-standing classical genetics of the orange trait, the rarity of male tortoiseshells and their usual association with chromosomal anomalies, and recent efforts to identify the underlying gene and the regulatory change that switches pigment production toward the orange pheomelanin pathway. It discusses how this sex-linked color has served as a textbook illustration of dosage compensation and mosaic gene expression.