[Cats] Saturday's trivia answer

[MJ]

Somewhere around 65-85% of blue-eyed, white cats are deaf.  White cats 
with non-blue eyes have about a 17-22% chance of being deaf.  White cats 
with only one blue eye have about a 40% chance of deafness. 
Interestingly, if a white cat with one blue eye is deaf in only one ear 
it's almost always deaf in the ear on the *same* side as the blue eye.

This prevalence of deafness in white cats is inherited.  The white coat 
pigment gene is what causes the deafness.  When a cat inherits the 
Dominant White gene (W) there is also a chance that the pigment cells 
within the ear can also be affected, resulting in deafness.  In the womb 
when the kitten is developing, this gene basically overrides color 
development and tells the cells to produce no color - which is what 
white is (absence of color).  With hereditary deafness, some kittens are 
born deaf, but others lose their hearing within a few weeks of birth.

Interestingly, the dominant white gene obliterates the "true" coat color 
of the cat.  In some white cats you may find a spot on the head or even 
a few stray hairs of a different color.  This is likely their "true" color.