If you're anything like me, you love our fluffy companions so much that you want to know how they inherited their beautiful coloration... just me? Ah well, it's still an interesting topic nonetheless! So buckle in as you learn why your cat looks the way it does! Note too, for this blog post I will capitalize gene colors like "Black" or "Orange", as it's a great technique I like to use to make the gene-coding easier to read.
Cats, just like humans, receive their genes from their mother and father and can be either XX or XY. Simple, right? Well, there are two "types" of fur determination genes they can get. The main one that is, truthfully, the easiest to understand is the Black gene. This gene, which is unrelated to the cats sex (important later) has three variations. Black fur (B), as it suggests, Brown fur (b) and Cinnamon fur (b1). They also display dominance, where Black is dominant over Brown and Cinnamon, and Brown is dominant over Cinnamon. So, if a cat has a B/b fur color, they will have Black fur and carry (not show) a Brown coloration that they can pass onto their offspring (Whiting, 1918). Now, there are dilution genes and super-dilution genes which do as they say and dilute these colors to Blue, Lilac and Fawn respectively, but their inheritance is another topic for another day.
To avoid confusion too, I'd love to add a quick side-note about piebald or white-spotting genes. A cat can have a large amount of white (but, usually, not completely white because that is a separate gene) or a very small amount, but that does NOT stem from the coat determination genes. It is a completely separate gene, so a purely black cat and a tuxedo cat can very well have the same coat determination genes (maybe B/B for example) and the only difference is the amount of white spotting they received from their parents on another gene (Whiting, 1918).
As an example to test your knowledge, think of two cats who are expecting a litter. The sire (male) has a B/b genotype while the dam (female) has a b/b1 genotype. What could their offspring look like? If you said some will be Black and others will be Brown, you are correct! For my Punnet Square fans, I completed one below. 
Now, some of you may be asking, what about your good ol' pet Fluffy, who is none of these? Well, ol' Fluffy must have the sex-linked O gene! The O-gene, which is attached to the X-chromosome, tells the cats fur to make pheomelanin, or an orange color. Now, the inheritance for this is is a little bit different, but stick with me! If an female cat that has an O gene (aka, has orange somewhere on her fur, because the gene always shows itself if present) and has a male offspring, the male may receive her X that carries the O gene and, as a result have orange fur too. Now, you may be asking, what if the tom cat has the O gene from mom but gets, say, black fur from the father? Well, the Black gene doesn't get shown! In males, the fact that they have XY chromosomes means that, if they get an X with the Orange gene, it completely covers any other color they may receive. So, male cats that get an O gene will only be orange (maybe orange with white, look at the white-spotting gene above). Kinda easy once you get it. Now, for females...
You may have heard that calico cats are primarily female, and you would be correct. Aside from genetic malfunctions, such as a male having XXY sex chromosomes, only females can be orange and black at the same time. Why? It's thanks to their two X's. If a female has one X that carries an O, meaning they have the Orange gene and will present some orange fur, but if she also has the other X carry o (or non-orange gene), then they will have their Black gene also present on their fur. A bit complicated, I know. But remember that the Black gene has three variations (Black, Brown and Cinnamon)? These can all combine with the Orange gene to make beautiful calico cats (or tortishell: a calico without any white)! Below are images of a chocolate calico and a cinnamon calico, respectively! Some of you may be asking, does that mean a female that has two X's both carrying the O-gene is rare, aka a non-calico orange she-cat? Rare is not the correct term, as it's not like a male calico and nearly impossible to get, but it is uncommon; something like only 20% of orange cats are female (Fitzsimmons, 2025).
Now, hopefully I haven't bored you. But cat genetics are a fascination of mine and I am always open to anyone with any cat coat questions emailing or private messaging me about your ol' pet Fluffy! Or, if people are interested, I'd love to do a second part discussing dilution genes, color point genes (I could go on-and-on about these) as well as eye color inheritance. And hey, in the words of the great Bob Barker, remember to spay and neuter your pets!
Works Cited
Fitzsimmons, P. Are All Orange Cats Male and All Calico Cats Female? | Chewy. (2025). Chewy. https://www.chewy.com/education/cat/training-and-behavior/behavior-pet-facts-are-all-orange-cats-male-all-calico-cats-female
Whiting, P. W. (1918). Inheritance of coat‐color in cats. Journal of Experimental Zoology, 25(2), 539-569.
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