If the orange color is sex regulated, how does it also appear on the females?
In: Biology
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Orangeness is determined by the O allele, which is on the X chromosome. O, for orange, is relatively uncommon and o, non-orange, is the majority of the cat population. For quick terminology review, a gene is the area of DNA that produces some protein, and alleles are the different types. O produces the protein that makes orange hair, and o doesn’t. Because we have two of most chromosomes, most of them (autosomes) we have in pairs, so the genes on those chromosomes also have two alleles in each of us, which can be the same or different. X and Y chromosomes are a pair too, but Y is tiny and doesn’t have much on it, so most of the chromosomes are only on X, and males only have one while females also have a pair of alleles.
Most cats aren’t orange or calico and have only one (male) or two (female) o alleles. If they inherit one O, males are orange but female most likely have O and o, so they are calico. A female with an orange father (O) and calico mother (Oo) can inherit two O’s and be orange. A cat with two orange parents (O and OO) will always be orange.
Calico happens because each cell in cats or humans has only one active X chromosome, and which one is active is random early in development but not at the beginning. So one chunk has O and a orangish, and another chunk is o and looks brown/black, and the mix produces calico.
I actually know about this! Certain colors of fur are definitely attached to the same chromosomes that determine sex. Specifically, the black color and the orange color are attached to the “X” chromosome. Like humans, female cats have two X chromosomes. The thing is, you can’t attach both the black and orange colors to one X chromosome. Therefore, because male cats only have one X chromosome, they (usually) can only either be black or orange. Female cats have two X chromosomes, meaning one can carry the black color while the other carries the orange color.
Okay, as far as the orange cat thing goes, I’ll try to explain so it doesn’t get confusing. If you want to produce an orange male cat, all you need is for that orange gene to attach to their X chromosome. For female cats, they can’t be orange unless BOTH their X chromosomes have the orange gene. So female cats can be orange, but it’s easier for a male cat to come out orange than it is a female cat (which is why most orange cats are male).
The genes that determine fur color in cats is in the X chromosome.
For male cats they only have 1 copy of those genes, so whichever version of the gene they get determines their hair color. Be it black, orange, tuxedo, grey, tabby, etc
For female cats they have 2 copies of those genes.
Cats actually have 2 versions of the orange haired gene, a dominant gene O and a non-dominant o.
For a female cat to be orange they need two copies of the O gene. If they have 2 copies of the o gene they up end up black. If they have O/o then they are a tortie. If the are O and another hair color they end up a calico.
This is because the O gene is isn’t fully suppressed by the other hair color gene. So as cells divide they have to pick one of the other resulting it splotches of different colors all over the cat.
The dominant A gene however tends to override any other hair color gene, which is why Tabby’s are so prominent. Tabby patterns are also the natural hair pigmentation of the African bush cat that domestic cats descend from.
Male calico’s do exist but they are very rare and are often hermaphrodites.
To make it short. The orange gene is in the female gene, and since males have one female (X) and one male gene (Y) they either have or don’t have the orange gene. A female has two female genes (X and X), so they can have one which is orange and one which is not, resulting in a partly orange cat.
Very simple version, cat X can be orange or black. Boys are XY so they can be X(orange)Y or X(black)Y. Girls are XX so they can be X(orange)X(black) to make tortoiseshell or have the white masking gene too to make calico and normal males can’t have two Xs. They have to be XXY or chimera.
More male cats are orange just because of random selection, it takes two orange Xs to make an orange girl so if you have a calico girl and black boy you can get orange boys but no orange girls. Orange girls need an orange or calico mom and orange dad. Since lots of cats are just breeding randomly you get pairings that can’t make orange girls.
Cats have a gene on the X chromosome that determines whether their fur contains dark or light pigment. There are two possible versions of this gene: one which causes dark color (brown or black), and one which causes light color (usually orangish).
Male cats only have one X chromosome, so they can only have one option. They’re either dark or orange. The Y chromosome simply doesn’t have this gene at all.
Female cats have two X chromosomes. If both of those chromosomes have the same version, the cat will be fully that color; but if she has one copy of each she will have patches of both colors.
Very very rarely (~1 in 3000 odds), a male cat can be born with both dark and orange patches. This can be caused by several things, but it requires some sort of genetic abnormality to happen.
[Here’s an entire Wikipedia article about cat coat genetics if you’re curious.](https://en.wikipedia.org/wiki/Cat_coat_genetics) There are many more genes that affect their coat- things like stripe pattern, whether the dark patches are brown or black, and the presence of white fur patches are determined by other genes.
There is an answer in this short video by Veritasium: [Why Women Are Stripey](https://youtu.be/BD6h-wDj7bw?si=ExnEPWN_dMHOh3nV). (It addresses calico cats, but not orange cats.)
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