Several weeks ago, some of our blogger friends made comments about blue eyes that had us reaching back to last summer. We located an article we wrote on blue-eyed cats, gave it an update, and posted it last Monday.
As a result, we got some great questions from you. Things like "is my cat an albino?" "what about odd-eyed cats?" and "people expected my white cat to be deaf but he isn't!"
Special thanks to the Kitties Blue at the Cat on My Head, to our Auntie Bernadette at the Creative Cat and Auntie Connie at Tails from the Foster Kittens (who, by the way, is visiting us right now - aren't you jealous?) for their input.
You guys had such cool comments that we decided to go find our Star Trek post from last year and update it!
Before we go all sci-fi on you and pull out our Doctor Who references, bear with us as we do some science (we'll make it painless. Uh, we hope....)
#1: There are 8 different
genes that determine what
a cat’s fur will look like.
Some of them are more basic, while others are what you’d call modifiers. An example of a foundational gene would be the Black Gene. Allie has this gene.
Huh? The girl’s clearly grey, not black. True.
But we’re not dealing with the black color, we’re dealing with the Black Gene – and it has 6 different settings. Take a look at the table below.
A cat with an active black gene fits into one of these categories. They’re either set on high beam or low beam (full density or dilute), but their coloring can also come in one of 3 different concentrations.
I mentioned modifiers. Some of these 8 genes don't determine the color of your cat. They change or overwrite that color. For example, the boys have the albino gene, which modifies coat color by turning the color off at certain temperatures.
If you want to read more in depth about the 8 different types of genes, click here to read our post from last summer on it.
#2: The White Gene
isn't a color gene.
It's a masking gene.
If a cat has this gene turned on, then the gene’s basically overwriting any color gene your cat has! This gene has three basic settings: low, medium and super-charged.
If the setting’s on low, it’s called a Gloving Gene. Like you’ve probably guessed from its name, it “puts gloves” on a cat - those cool white paw markings you see in some Ragdolls, Himalayans, and of course the Snowshoe cat.
|Genetically "white"? No.|
Golden eyes = Spotting gene.
Photo: Incanus Japan
In fact, often times a cat we think of as a white cat really isn’t. At least, not genetically speaking.
If there’s even one colored hair anywhere on a kitty’s body, then the cat doesn't have the White Masking gene – just a really active Spotting gene instead.
This kitty basically has one big white spot all over his body.
Enough already. Bring on the Tardis. Warp speed please!
Alrighty then! How's this?
Because the White Masking gene is responsible for masking all color everywhere, that means pigment is masked or blocked in the eyes as well. Interestingly enough, this phenomenon causes white cats who have this "W" gene to be deaf.
But not all blue-eyed white cats are deaf, you say. Most are, but not all. Correct!
For those white cats that are not deaf, there is a different gene at play - the Spotting gene we mentioned earlier. So, what makes a white cat with the "W" gene deaf?
Um. Come again?
Star Trek: the reason white cats are deaf
Okay, well, maybe we're stretching the truth just a teensy bit.
Here's what's going on:
There is a spiral-shaped cavity in the inner ear called the cochlea.
This is where sound waves are converted to electrical signals and sent to the brain for processing.
In order for those electrical signals to be transmitted upstream to the brain, ion balance needs to be maintained.
(Sounds like some kind of warp drive, doesn't it?
Like I said, Star Trek. I rest my case. ;-)
We have no idea what ion balance is, and if you figure it out please let us know,
because we're weird like that and love to get our geek on.
Bottom line here is, the thing responsible for maintaining this mysterious ion balance is a thin layer of pigment called melanin that coats the inside of the cochlea.
|Blue eyes, by Blue Ridge Kitties|
No melanin means no ion balance.
No ion balance means no sound transmission.
No sound transmission means complete deafness.
So there you have it: Star Trek - the reason white cats are deaf.
That's our story and we're stickin' to it!
|Odd-eyed Lily by Jason Farmer|
But what about odd-eyed cats? There are occasions where the Spotting gene does invade the cochlea and prevent the melanin layer from developing. But this is fairly uncommon.
In fact, 60-70% of all odd-eyed cats hear just fine, thank you. Any apparent deafness must be attributed to the fact that the cat is, well, ignoring you.
Shocking, I know.
Oh by the way, our Maxwell’s deafness isn’t caused by that. He’s got plenty of melanin in his ears!
His blue eyes are caused by the albino gene, and while that does turn off pigment in select areas of the coat and eyes, it leaves the melanin in the ears untouched. If you’d like to find out what caused Maxie’s deafness, you can read about it in 2011’s Less Adoptable series post on deaf cats here.
One last comment and we're done - honest! White cats are not albino cats. There are albinos, but they have the Albino Gene (the basic one, not the temperature-sensitive one) and feature pink pigmented eyes.
And...wait for it... true albino cats are not deaf. Go figure.
We sincerely apologize for our Mommy. She is SUCH a geek.
Pleiotropy: University of Richmond
Basic Genetics as Revealed by Cats (U of California at Berkeley)
Hartwell, Sarah. White Cats, Eye Colours and Deafness, Messybeast.com. Retrieved February 2007.
Click these links to read last year's posts for more info on why a Siamese's coat is pointed (and called a temperature-sensitive albino) ...
or the genetics of coat coloring and what causes the striking look of a tuxedo kitty!
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Giveaway is open until 12/31.