GENES DON’T LIE - White Spotted Gene — How Much White Is Too Much White?

You’ve probably seen them — those dreamy white-and-colour cats with just a splash of black on the head, or a tail like it was dipped in paint.

They’re called van or harlequin, and their colouring comes from a gene called white spotting — or ws for short.

But here’s the twist:

Not every cat with this gene looks the same.

Some have just cute little socks or a white belly…Others are almost completely white — and yet they don’t carry the gene for dominant white (w) at all.

So what’s going on?

Let’s break it down :

What is the white spotting gene?

The ws gene works a bit like a paintbrush — it tells the body where not to put pigment.

A cat can inherit:

• One copy of ws (ws/n) — and often shows a small-to-medium amount of white (like mittens, bibs, or tuxedo patterns).

• Two copies (ws/ws) — which usually results in a cat that’s mostly white, with just a splash of colour on the head and/or tail. That’s what we call a van pattern, or sometimes harlequin.

Types of White Spotting (FIFe EMS Classification)

In official cat registries, white spotting is classified using EMS (Easy Mind System) codes based on the amount of white:

EMS 09 — Low white (<50%)

Examples:

• Mittens

• White bibs

• Belly spots

• Tuxedo cats

EMS 03 — Bi-colour (≈50%)

Examples:

• Symmetrical white legs & face

• Half-white coat

• Classic half-white appearance

EMS 02 — Harlequin (50–75%)

Examples:

• Mostly white body

• 3–6 large colour patches

• Often on the back, face or tail base

EMS 01 — Van (>75%)

Examples:

• Colour restricted to head and tail

• Sometimes one or two small body spots

But…

Some cats with just one copy (ws/n) look like full van-patterned cats. Others with two copies don’t look very white at all.

Why?

Let’s talk modifiers (and beyond)

There are other genes at play that don’t create white themselves — but they affect how much white shows up. Think of them like volume knobs. They don’t produce white, but they control how loud the white spotting gene is. They explain why two kittens with the same ws/n genotype can look totally different.

Some of these include:

MITF, PAX3, EDNRB, SOX10 — genes that influence how pigment cells move during development in the womb.

They're not technically "modifier genes" in the scientific sense, but they do influence the expression of white. And this expression can vary widely between individuals.

The health connection

Why should we care how white a cat is? Because sometimes, it’s not just about looks.

Some of the genes that influence white expression are also involved in the formation of the inner ear and the development of pigment cells.

In some cats — especially those with extreme white spotting and blue or odd-coloured eyes — there may be an increased risk of hearing loss.

There’s growing evidence that some cats may even show a Waardenburg-like syndrome when combinations of certain genes (e.g. ws/ws , ws/n plus variants in MITF, PAX3, etc.) are present.

That’s why even cats that aren’t genetically "white" but show extreme white from ws should still be monitored.

Can we test for modifier influence?

Not with standard commercial panels. Tests like MyCatDNA, UC Davis, or Wisdom Panel won’t detect these effects.

But some breeders are turning to Whole Genome Sequencing (WGS) to understand what’s going on in high-white lines.

So what should owners and breeders do?

If you’re buying or working with van or harlequin-patterned cats, especially those with blue or odd eyes, don’t just assume they’re fine because they’re not "white" cats.

Ask for a BAER hearing test.

It’s safe, quick and non-invasive — and can detect full or partial deafness early.

Because sometimes, those beautiful kittens with soft pink noses and ocean-blue eyes…

…are only listening with one ear.

And every cat deserves to be truly heard.

#GenesDontLie #ICONICSX #WhiteSpottingGene #VanCat #HarlequinCat #ModifierGenes #SphynxEducation #BAERTest #KnowYourCat #SmartBreeders #CatGenetics #ResponsibleBreeding #WaardenburgAwareness #TransparencyMatters #DNAdeepDive

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