After more than 60 years of genetic guessing, scientists have finally cracked the code behind what makes orange cats so… orange. In two separate studies published on bioRxiv, researchers have identified a specific DNA deletion on the X chromosome that turns a regular cat into a fiery feline. The discovery sheds new light on how genetics drive fur color—and why orange cats are almost always male.
The Secret Sits In Silent DNA
The culprit isn’t a mutation in a typical gene that codes for pigment. Instead, the answer lies in a non-coding region—a stretch of DNA that doesn’t build proteins but controls how genes behave.
Researchers found that orange cats have a 5,000-base-pair deletion just before a gene called Arhgap36. This deletion causes the gene to become overactive, especially in melanocytes, the pigment-producing cells in skin.
Cats with this deletion produce more Arhgap36 RNA—up to 13 times more than cats without it. That overactivity shifts their fur color from dark black-brown to the reddish-gold we associate with marmalade cats.
How The X Chromosome Shapes A Cat’s Coat
The orange gene sits on the X chromosome, which helps explain one of the biggest quirks of orange cats: why most of them are male.
Male cats only have one X chromosome. If they inherit the version with the orange gene, they become fully orange. Female cats, on the other hand, have two X chromosomes—one from each parent.
In female cats, one X chromosome randomly turns off in each cell. That leads to a patchwork of fur colors, often creating tortoiseshell or calico coats. Only if a female inherits two copies of the orange gene will she turn out completely orange—a rare event.
What’s Really Behind Calicos And Tortoiseshells?
Calicos and tortoiseshell cats are genetic mosaics, and the orange gene plays a major role in that. But there’s another twist: a white-spotting gene.
Tortoiseshell cats have intermingled patches of black and orange. Calicos have larger color blocks separated by white fur. That white comes from a gene that affects how pigment cells migrate and survive as the kitten develops.
So even when the orange gene is present, its visual effect depends on how these other pigment genes behave.
Are Orange Cats Really “Goofy”?
The internet loves to joke that orange cats are lovable but a little less sharp. And while orange tabbies have a reputation for being clingy, chaotic, or not-so-bright, there’s no science to back that up.
The Arhgap36 gene has known roles in development, but in cats, it seems to only activate in skin pigment cells—not the brain. That means orange fur isn’t linked to intelligence or behavior.
Still, human perception plays a big role. Because orange cats are so visually distinct, we might be more likely to assign personalities to them—whether or not those traits are real.
A New Chapter In Feline Genetics
These new studies don’t just solve a long-standing mystery—they mark a turning point in how scientists understand non-coding DNA. For decades, researchers focused mostly on protein-coding genes.
Now, this discovery shows how even the “quiet” parts of the genome can have big effects. And there may be more to uncover. Orange fur was just the beginning.
