I can take a guess. The calico parts are extremeties, tips of the feet, ears, and tail? In some cases, cat coloring can vary based on the temperature at that part of the body: In cooler parts (the extremities), one gene is active, while in warmer parts (the core, subject to more body heat), the other one is (this is what causes the distinctive Siamese coloration). So I can imagine that maybe, in the warmer parts of your cat, one of the genes is deactivated by the heat, leaving just the tabby coloring, while in the cooler extremities, both are active, producing the calico pattern.
While Siamese coloration works like that, I don’t think calico would. However, without seeing the cat, it would be hard to know what it’s genetics might be.
See the link I provided in post #7 for a very detailed explanation of many of the genes involved in cat color genetics.
Am I correct that the majority of tortishell cats are male?
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Like others have said, tortoise-shell cats are just calicos without the white. The white gene isn’t on the sex chromosomes. So, in order to get one X chromosome with orange and one X with black, you have to have a female or an XXY male.
Having just had a class on this from the state’s (nation’s?) leading researcher on animal coat color genetics, yes. Yes, yes. IIRC, there are no coat colors associated with the sex chromosomes in dogs or horses. There are some coat colors associated with different disease processes, but this usually has to do with the migration of melanocytes, the cells that make skin and hair pigment, and not precisely the color itself.
Close, chronos, but you are getting your cat coat color dynamics confused.
I’m guessing from the description that SCSimmons has a cat that looks like this or this
These are usually the cats with “calico tabby” coloration, with varying degrees of white. So long as the cat is orange, some other color, and white, it’s a calico. Here’s how it works:
Orange is on one X chromosome. Black is on the other. In these kitty’s cases, instead of black, they have brown. Brown is an allele, or variation, of the black color gene. So, instead of being orange and black, they will be orange and brown. Now, to make things complicated, on a completely different chromosome is a gene that tells the color genes to make stripes instead of solid color. If the patches are big enough, the stripes are really noticable, like on the kitty in my second picture.
The melanocytes, or the cells that make pigment for hair and skin, radomly choose which X chromosome to use. Once they decide, all of their daughter cells will use the same X. That’s why there are patches of orange and brown. In SCSimmon’s case, most of the cells went with brown, while only a few chose orange, just like the cat in my first link, who only has a few patches of “calico” while the rest is “tabby.”
The fun part is the white. Yet another gene tells the kitty’s body how many melanocytes to make while it is still an embryo. Sometimes, the gene only tells the fetus to make a few melanocytes. These cells then migrate down from the spinal region of the embryo. The white patches are areas that the melanocytes never reached. This is why the white patches tend to be on the tummy and toes. But some calicos are almost completely white. They only made a handful of melanocytes.
The heat reaction that you describe, Chronos is how the color patterns for Siamese cats happens. In their case, the white patches are not because there are no melanocytes, but rather because the melanocytes make a defective pigment protein. Like you said, this protein is heat sensitive, and doesn’t work on the parts of the cat’s body that are warm. That’s why the ears, feet, and tail are dark: they’re colder compared to the torso. If you were to shave a Siamese cat, on it’s side, the first fur that grew back in would be dark. It would later lighten as that part of the skin regained normal temperature. If you shaved your calico, the color would come in exactly as it was before.
I’m sure you have this a bit off, IIRC black and orange are co-dominate, which in females will produce the calico/tortious shell patern.
Orange is not a (sole) dominate color for cats, if you see a orange cat, chances are that it is male, since a female needs both orange pairs to actually be ornage, while a male needs only one (since it’s on the sex XX or XY pair)
Damn, I was starting to get excited about having a male calico cat until I went back and looked at the pictures! Here a calico is a very pale ginger cat.
Actually, it’s a bit more complicated than that. Black and orange are not co-dominant; which would mean that the phenotype would be intermediate between orange and black. Instead, orange is at a different locus than black, and is epistatic to it; that is, it masks its effects.
From the site I linked to in post #7:
Note that the dominance referred to here is only with respect to the other two alleles at this locus, not to other loci.
Orange is “dominant” to black, even though they are not at the same locus. In the absence of orange, black is dominant to (some) other colors; there is also a Dominant White gene, one of three genes that can produce white coat colors.
You are however correct about the sex-linked part with respect to orange.
