Mystery of Ginger Cat Is out of the Bag

The genetics behind the vibrant orange color in feline coats is finally confirmed after 112 years

- TOM HOWARTH

FOR MORE THAN A CENTURY, the genetic secrets behind the vibrant orange coats of ginger cats and the intricate patterns of tortoiseshells have puzzled scientists and cat enthusiasts alike.

Now, two studies have finally identified the genetic key to this mystery, solving a puzzle first theorized in 1912. The studies, conducted independently by Japanese and American research teams, have pinpointed the gene responsible for orange coat coloration in cats: ARHGAP36, informally dubbed the “orange” gene.

This discovery not only confirms a 112-year-old hypothesis, but also sheds light on a new biological pathway involved in pigmentation.

In 1912, American geneticist Clarence Cook Little proposed a visionary idea linking coat color inheritance in cats to the X chromosome.

His theory suggested that orange coat color was controlled by a variant on the X chromosome, explaining why ginger cats are mostly male and why tortoiseshell cats, with their mix of orange and non-orange fur, are almost always female.

Little’s hypothesis predicted that males, having only one X chromosome (XY), could only be fully orange or non-orange, while females (XX) could inherit one of each variant, resulting in the tortoiseshell pattern.

He also calculated that ginger females, needing two orange variants, would be relatively rare.