Sex-linked orange coat colour in cats is associated with an approximately 5 kb deletion in the ARHGAP36 gene, located on the X chromosome. This variant causes abnormal ARHGAP36 expression in melanocytes, reducing the production of eumelanin, the black-brown pigment, and promoting pheomelanin, which is responsible for orange coloration. Males, which have only one X chromosome, are orange when they carry the O variant, whereas they do not show this colour when the variant is absent. In females, two copies of the variant produce an orange coat, while a single copy leads to mosaic expression of orange and non-orange areas, resulting in tortoiseshell or calico coat patterns.

Transmission

Breed