I knew that female calico cats are quite rare, but someone told me that orange cats which are female are rare also.
Is that true?
I hardly ever SEE any orange cats lately.
Good grief, where do you live? Antarctica?
It’s male calico cats that are exceedingly rare, and female orange ones – cat fanciers call that colour “red,” by the way. When you look closely at a calico or tortoiseshell cat, you will see that the red patches are actually red tabby patches. And indeed, at least one parent of a litter including such cats will have tabby genes.
The gene that produces tortoiseshell (red tabby and black), calico (tortoiseshell and white), and red and red-and-white cats is sex-linked. According to Desmond Morris in “Cat World”, the likelihood of finding a male tortoiseshell cat is calculated at 200 to one, and that lonely creature will be sterile. The master goes on thus:
"What makes the sex distribution of these cats so odd is that normally only a female kitten can display black patches inherited from one parent and red tabby patches inherited from the other. This is because the genes controlling these particular colour forms are both carried on the X chromosomes, the red gene on one and the nonred gene on the other. The catch is that only females have two X chromosomes, so only females can display the “red plus nonred” tortoiseshell combination. Males have instead an X chromosome and one small Y chromosome, which means that on their single X they carry either the red or the nonred gene, but cannot have both. So they are either all-over red tabby or all-over black.
“If this is the case, it is hard to see, at first glance, how male tortoiseshells can exist at all. The answer is that occasionally there is a minor genetic error and a male cat develops with the genetic combination XXY. The double X gives it a chance to be red and black, while the Y chromosome gives it male characteristics. It does, however, have a problem because its masculinity leaves a lot to be desired. To start with, it is sterile. Also, its behaviour is extremely odd. It acts like a masculinised female rather than a true male. …” (entry for Tortoiseshell, p. 448)
Actually, most calico cats are female. Occasionally there’s a male, and–I believe–they are generally sterile.
What’s odd, though, is that there are indeed very few female orange cats. This is seemingly contradictory because both orange and black colors are both carried on the X chromosome (which explains whey there are more female calicos than males–a male would need to be born with a genetic XXY abberation). Maybe someone with some expertise in feline genetics can explain why.
Back to Desmond Morris:
"Red. Coat colour. Red is the cat breeder’s name for the colour that geneticists call orange. All the vbarious “red-tone” colours, such as yellow, marmalade, orange and red, are controlled by a single sex-linked gene, designated O for orange. The effect of this gene is to convert all black pigment to orange. This means that it converts an ordinary tabby pattern into orange tabby. … " (“Cat World: A Feline Encyclopaedia”, by Desmond Morris. New York: Penguin Reference, 1997. P. 359)
The article then goes on to explain how selective breeding is done to darken the naturally ginger colour and reduce the stripiness of the tabby markings.
In a tortoiseshell or calico female, the black pigment gene on the other X chromosome is not affected by the red gene, I presume.
If female orange cats are rarer than male orange cats, then I would guess that it’s just because female calicoes are more common than males. In other words, if a (chromosonally normal) male cat has an orange gene, then he’s orange, because there’s no room for other color genes, but if a female cat has an orange gene, then she might be orange, or calico, or tortoiseshell, or presumably some other combinations, depending on what the other gene is.
Just my 2 cents…
I happen to have a female orange tabby cat, very sweet. When I was looking for a kitten, I purposly looked for an orange tabby because they (in my experience) have very good temperments. They are not rare, it was easy to get one at the local animal shelter.
Maybe when the OP refers to an “Orange” cat, they are refering to somthing different than a common orange tabby?
The reason why calicos and tortoise shell females exist is due to the fact that female mammals are mosaics.
Tortoiseshell cats are the best example of mosaics. One X chromosome of these cats contains the black gene (B) and the other contains the yellow/orange gene, (Y). Females have two X chromosomes, but in any given cell, only one is active. Both can be transcribed during cell division, but only one “shows” it’s effect in the animal.
Sometime during early embryonic development, one of these chromosomes is turned “off”, and it’s effect is not seen. This inactivation is totally random, and is usually done in the first couple weeks of development.
What this means, is that in cells where the B is turned off, the yellow skin/hair pigment is visible, and where Y is turned off, the black pigment is visible. Since this is a totally random effect, there are no two identical tortoiseshell cats - not even in twins.
Calico cats exhibit the same mosaic pattern, however they also have white hair in patches. This is due to a separate, non-x-linked (autosomal) gene, which I think behaves by normal Mendelian patterns, but I’m not sure.
Humans are also like this, though there are very few x-linked genes that have a noticeable effect like in cats. I don’t remember the name of the disease, but one effect is a problem with the sweat glands (I believe they are inactive). Hence, while a male would have this exhibited on his entire body, a female only has it in patches, such as a patch on the arm, chest, and leg, but normal everywhere else due to the inactivation of the chromosome having the deleterious gene. I’ll look up the disease name tomorrow.
Boy, am I now ever glad I went to Genetics class on Friday. All this spewed back out at you guys without looking at my notes! Think I’ll pass my midterm in a few weeks? 
Sorry,
In my OP, I meant to say male calicos.
Yes, I meant orange tabbies of course.
So…are you saying that male calicos are gay? Kidding.
I love orange tabbies, my son insists on getting one when we get a kitten.
We live in a condominium complex and almost everyone has cats.
We have visited many of these cats; my son insists on my going up and knocking if he sees a cat at the window and then we make new friends.
None of these cats have been orange. It just struck me as odd.
We see tons of gray tabbies but hardly any orange ones.
Here’s my own calico, Piper. Note the orange, black and white. Note that she’s female.
You can’t see it in this photo, but the backside of her head is divided almost perfectly between orange and black, with the line between them corresponding almost perfectly to where her corpus callosum must be.
I also own two of her brothers, neither of whom has any orange at all.
Five, she is absolutely beautiful!
I printed the photo for my son, who Loves cats.
He is, by the way, a male.
vanilla:
Thanks, I agree.
Your son is male? Well, I kind of figured.