Mosaic Cat Has Identity Issues
Irradiated by LabRat
I have NOTHING to say. Be it the weather, the Lazy Sunday mood, or the horrifying prospect that I’ve made a horrible mistake and expended my entire life allotment of Being Moderately Interesting with this reckless blogging experiment, I haven’t been able to muster up much beyond a one-sided shoulder shrug and the sentiment “I’d rather be drinking beer and watching Ninja Warrior” on much of any subject.
Over in the comments of Tam’s latest update on her move-traumatized kitties, there seems to be some discussion on why tricolored cats are always female. So hey, a question I can answer- let’s turn it into blogfodder.
Tricolored cats are always the same three colors- black, orange, and white. Any cat can be black and white or orange and white, or any other base coat color and white; the white spotting (or, to use fancy coat-color language, “piebald”) gene is a dominant with varying expression depending on how many copies of the gene the kitty is toting. Two piebald doses gets you a cat that is mostly white, one gets you a cat that maybe just has white paws or a “tuxedo”. The gene acts like a bleach for the color that would normally be there, and also causes the “odd-eyed” effect- bleaching out the eye color on one side from whatever the normal shade would be to blue but less completely on the other. Since melanin (a color pigment) is essential to the proper development of the nerves in your ear, this gene can also cause the deafness common to blue-eyed white cats. Complete whiteness is also caused by another dominant gene; it is possible to have a cat that, genetically speaking, is a white-spotted white cat.
There are really only two coat colors available to cats: black (melanin-pigmented), and red (phaeomelanin-pigmented). Every other coat color is caused by some modification to Basic Black or Basic Red; genes for ticking, tabbying, spotting, bleaching, colorpointing, shading, or dilution. The allele that determines whether a kitty starts with a ground state of “black” or “red” is sex-linked, or X-linked if you want to use language that’s a bit clearer- it’s on the X chromosome of the chromosome set that determines sex in mammals. This is why normally, tricolored- or bicolored with black and red- cats are always female: males only get one copy of the allele, since the other chromosome in the pair is going to be a Y with no copies of that allele at all. When male calicos and tortoiseshells do appear, they’re mutants- genetically XXY sterile individuals. (In humans, this is called Klinefelter’s Syndrome.)
So, why the patchy pattern? Black and Red are both simple dominants- there isn’t going to be any median shade between them; either one is fully expressed or the other is. The reason a cat with two X chromosomes and a different coat color on each winds up with both is that, depending on the patch of fur you’re looking at, either one chromosome or the other is inactivated and there’s only one color TO express, so far as that area’s cells are concerned. For all mammals, early in the life of every female embryo, in every cell present at the time one X is inactivated, and every cell that goes on to multiply from that original cell will have the same pattern of activation. Which X is flipped off is completely random, which is why tortoiseshell and calico cats have such unique patterns. Every female mammal alive is a genetic mosaic with one chromosome active in some of the cells of her body and the other in other places- it’s just that with cats, the pattern can be strikingly visible.
As for the other question in that thread- are torties and calicos crazier in greater proportions than other cats- I couldn’t comment. I know that when I worked for a vet, we had plenty of color stereotypes- the torties and calicos are crazy, the black ones are more aggressive, the orange ones are sweeter- and I can’t really say that, in my view, they were justified. We had sweet black cats and nasty orange ones, and sweet calicos. I do have my own predjudice, though- I think the females do tend to be higher-strung than the males- and that could be the origin of the stereotype.
March 9th, 2008 at 11:47 pm
Interesting. When I worked at the Humane society, it was common knowledge that the brown and gray tabbies are the ones that will eat your face. Torties and calicos were sweeties!
Also, there’s a cat at my work now who must have some bizarre genetics. He’s got way too many toes on some feet, only two toes on one foot, and deformed legs (it looks like his knees are in the wrong place…?). We call him “Roo” because he hops around like a kangaroo. He gets around okay, is friendly with people, and can even jump up on tables like a regular cat, but he looks very strange.
March 10th, 2008 at 6:46 am
Well, I’ve had several Calico’s and without exception they were all insane. They would turn at a moments notice and you never knew when that would happen. they would be all lovely dovey and pet me play with me then turn into a raving lunatic trying to remove parts of your anatomy. I finally went with the american standard. and I now have 3 of them 1 long hair female, 1 short hair female and 1 short hair male. The long haired female is nicknamed psychokitty for her habit of running through the house at 3 in the morning and literlly bouncing off the walls to change her direction. she also loves bubble baths, and loves to sit on high places and batt your head as you walk by.
March 10th, 2008 at 5:21 pm
I have a very sweet snuggly calico. She has some quirks…but what cat doesn’t, really?
March 10th, 2008 at 6:33 pm
Mittens is a tricolor calico and is, by the vote of nearly everyone who has met her, The Sweetest Cat On The Planet. She’s even-tempered, not cat-aggressive, and loves every human she meets instantly and unreservedly.
Random Numbers, a bi-colored tortie, lives up to her name, with a mercurial temperment and a high-strung hostilitity towards other animals, although she’s fine with people after a brief introduction.
Interestingly, one color stereotype I’ve always bought into that runs counter to those you shared concerns red tabbies: The legend I know credits them with being, and I quote, “Meaner than a striped-assed snake.” The slit-eared 25lb red tabby tom I used to own apparently bought into it too…
March 12th, 2008 at 1:07 pm
Ever since learning why boys are more likely to be mildly colour blind, i’ve had a love for this gene expression stuff. This one is also brilliant! I’m interested in what this random X-choice does in us humans, any ideas?
March 12th, 2008 at 3:53 pm
Well, the inactivated X becomes something called a Barr body, which before more advanced DNA testing was used as a gender check in international sports competitions- and about 1 in 400 “women” failed it.
The idea that X inactivation in humans could have more effects than just the Barr body seems to be a relatively new idea… which means most of it seems to be in journal articles I don’t have access to. I did run across one interesting theory, though; the idea that women have so much higher risk for autoimmune disorders (in which the immune system attacks the body) because there’s a possibility that certain structures associated with the immune system could wind up mostly or entirely with one active X, and the cells that control the immune system might therefore have a chance of not recognizing cells with the other X active as “self”.
March 12th, 2008 at 7:51 pm
Interesting. We had one enormous orange tabby that was OK with us - so long as we only petted him when HE wanted to be petted. The rest of the time he was a professional hunter and dog-terrorizer. You’ve heard the expression, “Dogs have owners, cats have staff”? That was him! (Which leads me to ask, are there any known incidences of cat/raccoon crossbreeding? I’d really like an answer to that one. I have my reasons…)
A second cat we had was a classic tortoiseshell - and nuttier than a peanut factory. Interesting to hear that this is not uncommon among cats of that phenotype.
March 12th, 2008 at 8:04 pm
Cats and raccoons can’t interbreed. Raccoons are in a genus (Procyon) that took the other main branch of two available in the history of order Carnivora. They’d be more genetically likely to be able to interbreed with a hyena.
However, they CAN interbreed with bobcats, lynx, and a number of other wild small cats.
March 13th, 2008 at 1:11 pm
Thanks, that’s an interesting theory indeed!