Cat lovers, you were right all along—the gingers really are special. While plenty of mammals have orange or red hair, only in domestic cats is the coloration correlated with sex. Now, researchers at Stanford Medicine have pinpointed the genetic mutation responsible: a small genetic deletion that increases activation of a nearby gene in cats’ pigment cells. This rogue expression disrupts the color-making process, swapping out brown and black pigments for a marmalade shade.
The mutation—known as sex-linked orange—is located on the X chromosome, giving males the advantage: They need only one copy of the gene in order to go full ginger. Females, with their pair of X chromosomes, need two; having one will result in patches of pumpkin, as in calico or tortoiseshell coloring.
Sex-linked orange is an example of how genes acquire new functions that allow for adaptation, Christopher Kaelin, PhD ’06, a senior scientist in genetics and lead author of the study, told the School of Medicine. Studying it helps scientists understand the emergence of physical traits in various species. And while tangerine cats are known for being lovable goofballs, Kaelin suggests that’s because most of them are male—there’s nothing to show that personality has to do with hue.
Jennifer Worrell is the copy chief for Stanford. Email her at jworrell@stanford.edu.
