Orange Fur Created By A Unique Mutation In Domestic Cats

A small deletion within a gene on the X-chromosome has unique effects upon cats' fur color, creating orange male tabbies and orange patches in female tortoiseshell cats.

Tortoiseshell Cat. (Credit: Shutterstock, via Chris Kaelin)

It was long predicted that the source of domestic cats’ distinctive pumpkin-orange fur coloring was genetic and was produced by a gene on the sex-determining X-chromosome because 80% of orange cats are male — so the trait’s mystery gene came to be known as “sex-linked orange”.