People ask why white cats with blue eyes are deaf. Not all of these cats are deaf (see part 2 of this short article).
Coat color and an aspect of the cat’s personality or another aspect of anatomy can be linked if the gene that dictates the cat’s colour and a gene which affects the way the brain develops are situated close together on the same chromosome.
If two genes occur on different chromosomes there is a random chance that the offspring (the kittens) will receive any particular combination of the two.
When two genes occur close together on the same chromosome they tend to be inherited together. I say ‘tend to’ because it is not certain.
In totally white cats, the gene that causes the cat’s coat to be white all over, the dominant white gene, is located on the same chromosome and is close to another gene which causes both eyes to be blue and the cat to be deaf (read about deafness in cats).
These genes are inherited together. It seems therefore that the gene that makes the cat white also makes the cat deaf and have blue eyes but this is no so. Indirectly the gene that creates the cat’s color also affects deafness and eye color.
Source: Cat Sense by Dr John Bradshaw. My thanks also to Sarah Hartwell.
Part 2 – Prevalence of white cat/blue eye deafness
White cats with two blue eyes have a 85% – 64.9% chance of being deaf in both or one ear. White cats with one blue eye (the other is usually yellow or gold) have about a 40% chance of being deaf in both or one ear. White cats with no blue eyes have about a 19% chance of being deaf in both or one ear.
Source: AETIOLOGY, PREVALENCE AND DIAGNOSIS OF DEAFNESS IN DOGS AND CATS by George M Strain published in this instance by Science Direct (the study).