Start researching cat genetics and you’ll quickly realize it gets complicated. But there are so many amazingly cool things to learn about how cats get their coat colors, it seems like I’m doing a disservice to you for not discussing it. I’m breaking down cat genetics into simple terms and examples, so you don’t need a science degree to understand them.
QUICK NOTE FOR ALLELE FANS: Alleles are variations of a gene. To keep things simplified in this article, I’m just referring to alleles as genes. I’ve included references at the end so you can explore cat genetics more if you’re interested.
The Basics of Cat Genetics
Before we dive into everything, you’ll need a really quick and basic science lesson on chromosomes and genes.
Just like humans, cats inherit half of their genetic make-up from their mothers and the other half from their fathers: 19 chromosomes from each, totaling 38.
The chromosomes X and Y determine sex. In mammals, normally females have XX chromosomes and males have XY. Some genes that contribute to color are on the X chromosomes, making them sex-linked genes.
On each chromosome, there are a bunch of genes that determine all the aspects that make up the living thing, including physical appearance. Genes can be dominant or recessive. Think about it as an argument:
The dominant is loud. A dominant will be represented if it’s inherited from one or both parents. The recessive is quiet. But, if both parents provide a recessive gene, then the recessive trait is represented.
You can also think of it as a convo. For example, the cell asks the pattern genes, “Should I be striped or solid?”
Gene from mom yells, “Striped!”
Gene from dad whispers, “Solid.”
The cell doesn’t even hear the whispering recessive gene from dad. As a result, the cell becomes striped.
Now, we’re ready to look at some cool traits about cats’ fur colors and patterns.
Colors: Orange & Black
Firstly, all cats originate from two colors: orange and black. The orange gene is just orange (O), but the black gene (B) has recessive versions, causing a cat to be chocolate (b) or cinnamon (b’). If these colors are represented, it means the cat also carries the dominant dense gene (D), but there are lighter variation of all these colors when another gene is present …
The Dilute Gene: Gray, Buff, and More
“But my cat is gray!”
Yes, because there is another gene that is recessive, the dilute gene (d), which lightens a color. Because it’s recessive, it must be inherited from both parents to be represented. With the dilute gene:
- Orange turns to cream/buff
- Black turns to gray/blue
- Chocolate turns to lilac/lavender
- Cinnamon turns to fawn/light lilac
If a cat is dilute, they may also carry a dilute modifier gene (Dm), which is dominant, and makes their dilute color even lighter:
- Cream/Buff turns to apricot
- Gray/Blue turns to blue-based caramel
- Lilac/Lavender turns to lilac-based caramel/taupe
- Fawn/Light lilac turns to fawn-based caramel
White is something different and more complicated (yay!), and I’ll explain it shortly.
Sex-Linked: We Love Our Gingers
As I mentioned earlier, females carry XX chromosomes, and males XY.
Now, it gets crazy: The orange color gene is only carried on the X chromosome, and the gene will tell the cell to “Go orange.” or “Go black.” The Y doesn’t have a gene for color.
Why does this matter?
Because for a female to be orange, she must inherit the orange gene from both parents on each X chromosome, and then her genetics tell her cells, “Go orange.”
Since the orange color is on the X chromosome and there is no color on the Y, the male only needs to inherit orange once. That’s why 80% of ginger cats are male.
Calcios & Torties Explained
Because females have XX, it’s possible that they carry the orange gene on one X and black on the other.
So which is dominant? Not so fast, cat genetics are about to get a little more complicated.
When there are two X chromosomes, only one X chromosome in each cell becomes deactivated. The body doesn’t allow both to be active. During embryonic development, some cells are told at random, “Go orange.” while others are told, “Go black.” Then those cells multiply.
The result? Patches of orange and black fur, resulting in a tortoiseshell or a calico (if the cat has the white spotting gene; don’t worry, we’ll get there). And because the color is random, the pattern of every tortie or calico is unique.
There is no color on the Y chromosome. A male can only have the color on the X chromosome of orange or black, not both.
But wait, there’s more.
The Rare Male Tortie or Calico
If a male is a tortie or calico, it means he has an extra X chromosome, carrying XXY, where one X has the black gene and the other orange. This is what I call a genetic oopsie, and it means the male is always sterile. In addition, these males often suffer from Klinefelter’s Syndrome, a disease that can cause cognitive and developmental issues, arthritis, diabetes, frail bones, higher body fat leading to heart disease, and ultimately a shorter lifespan.
What’s the Deal with White?
Next, let’s talk about white cats and how they get their beautiful fur.
White Spotting, I Didn’t Forget About You
White in calicos or bicolored cats (cats with white + something else) is from the white spotting gene, not the color gene. Males and females can have white since spotting isn’t sex-linked.
A cat will have white spotting if they inherit the white spotting gene (S) from at least one parent. How it works:
- ss – No white spotting
- Ss – White spotting on areas like feet, nose, chest, and tummy.
- SS – White spotting will cover more than half the body. Small chance cat will be completely white!
Why not complicate things more?
I’m glad you asked.
Good Golly, Miss Dolly
Usually, solid white cats have the dominant white gene (W). One of the coolest things, is that this gene is masking the actual color of the cat.
When a dominant white kitten is born, you’ll see a few head hairs that are a distinct color. They disappear after a few months. My resident cat Dolly is a dominant white, and I know that because she had a few black hairs on her head as a kitten, which I used to joke were her grays. This means Dolly is actually a black cat.
White vs. Albino
How are albino cats different from white cats? Albino cats are born with a missing or damaged TYR gene, so they lack the enzyme that produces melanin, tyrosinase. Their genetics contain literally zero color. White cats simply have less melanin than cats of other colors, plus their genetics still contain color.
Albinos to have no pigment, with pinkish skin, and the palest blue eyes, which also appear pink sometimes. The pink color is light reflecting off blood vessels in the eyes and blood flow under the skin.
FUN FACT: There is such a thing as a partial albino. The pointed pattern of Siamese, Burmese, and Tonkinese cats has its roots in partial albino lineage.
Are Black Cats Healthier?
Don’t worry, I didn’t forget about black cats, who get their gorgeous color from the B gene. Scientists have discovered that genes associated with black fur and excess melanin in cats also provide stronger immune systems. Black cats are more resistant to FIV (feline immunodeficiency virus aka feline HIV), than other cats. Scientists hope to map the genome for black cats and panthers to get closer to a cure for HIV.
Tabbies: Obvious or Undercover?
Domestic cats all cats carry the tabby pattern somewhere in their genetics.
The A gene is responsible for patterns on cats.
- A or agouti, dominant, creates a ticking or band of colors on a hair.
- a or non-agouti, recessive, creates a solid-colored hair.
A cat only needs to inherit the dominant A from only one parent to get the tabby pattern, making most cats tabbies.
How do you tell if your kitty is an undercover tabby? Look at their tail, legs, and head when they’re laying in the sun. The stripes are called ghost tabby markings.
All Gingers Are Tabbies
Another note on color.
The easiest explanation for why all orange cats are tabbies, is that solid orange is just not possible with the genetic makeup of cats.
The slightly deeper explanation is some genes, called ecstatic genes mask other genes. The orange gene is ecstatic and ALWAYS overrules the solid non-agouti gene, “No, you can’t be solid. Boy, bye.”
Well, you made it to the end! Thank you for reading my breakdown of colors and patterns in cats. I hope you learned something, and if I confused you, don’t worry – it’s confusing! Please reference my resources to learn more.
Did you catch my post on affordable cat litters that don’t stink? Check it out.
Learn More About Cat Genetics
Basic Genetics as Revealed by Cats, ib.berkeley.edu.
Cat Chromosome Information, by Heidi Wiesenfelder, sciencing.com.
The Genetics of Calico Cats, bio.miami.edu.