Since a large variety of different coat patterns exist within the various cat breeds, the cat is an excellent animal to study the coat genetics of hair growth and coloration.^[69] Several genes interact to produce cats' hair color and coat patterns. Different combinations of these genes give different phenotypes. For example, the enzyme tyrosinase is needed to produce the dark pigment melanin and Burmese cats have a mutant form that is only active at low temperatures, resulting in color appearing only on the cooler ears, tail and paws.^[70] A completely inactive gene for tyrosinase is found in albino cats, which therefore lack all pigment.^[71] Hair length is determined by the gene for fibroblast growth factor 5, with inactive copies of this gene causing long hair.^[72]

Cats have excellent night vision and can function at only one-sixth the light level required for human vision.^[44] This is partly the result of cat eyes having a tapetum lucidum, which reflects any light that passes through the retina back into the eye, thereby increasing the eye's sensitivity to dim light.^[45] Another adaptation to dim light is the large pupils of cats' eyes. Unlike some big cats, such as tigers, domestic cats have slit pupils.^[46] These slit pupils can focus bright light without chromatic aberration, and are needed since the domestic cat's pupils are much larger, relative to their eyes, than the pupils of the big cats.^[46] Indeed, at low light levels a cat's pupils will expand to cover most of the exposed surface of its eyes.^[47] However, domestic cats have rather poor color vision and can only see two colors: blue and green, and are less able to distinguish between red and green,^[48] although they can achieve this in some conditions.^[49]