PART THREE: The Recessive Genes That Shape Our Breeds

From colour to coat to pattern — the quiet genetics behind iconic cats

Recessive genes don’t just create pretty colours — they’ve shaped entire breeds, defined breed standards, and even influenced the rise of whole cat groups like the Siamese, Burmese, Rexes, and Sphynx. Many of the traits we take for granted today only exist because generations of breeders protected — and understood — recessive inheritance.

This blog explores some of the most important recessive genes in pedigree cat breeding, what they do, and why they matter.

🔹 1. Dilute (dd) — The Soft-Colour Gene

What it does: Lightens pigment, softening colours.

Full Colour	Dilute
Black	Blue
Chocolate	Lilac
Cinnamon	Fawn
Red	Cream

Genotype:

• D- = Full colour

• dd = Dilute

Why it matters: Dilute cats only appear when both parents pass on the recessive “d”. Without carriers, colours like blue, lilac, cream, and fawn could vanish from a breed.

A litter of kittens with chocolate (top left and bottom left) and its dilute lilac (bottom right) and a blue (centre) dilute of seal (mid right).

2. Longhair (ll) — The Fluffy Factor

What it does: Slows the rate of hair growth, creating long coats.

Genotype:

• L- = Shorthair

• ll = Longhair

Breeds influenced: Ragdoll, Persian, Birman, Maine Coon.

Key point: Two shorthaired parents can produce longhair kittens if both carry l — a classic “surprise litter” scenario.

3. Colour-pointing — Siamese, Burmese & Tonkinese

This is one of the most defining recessive systems in cat history.

Genotype	Appearance
cs/cs	Siamese point (blue eyes, stark contrast)
cb/cb	Burmese sepia (warm, even shading)
cb/cs	Tonkinese mink (moderate contrast)

Why it's recessive: Both alleles (cs or cb) must be present in a matching pair to override full colour.

Fun fact: Pointing is temperature-sensitive — cooler areas (ears, tail, paws, face) go darker.

NOTE: Mandalays are a solid colour variant of a Burmese as they're C/C or C/cb and Orientals are a solid version of a Siamese as C/cs or C/C.

4. Curly Coats — Multiple Recessive Mutations

Not all curls are created equal.

Devon Rex

• Genotype: re/re

• Coat: Wavy, soft, sparse

• Note: Devon curl is recessive only within its own gene system

Cornish Rex

• Genotype: r/r

• Coat: Fine, tight waves

• Important: A Devon crossed with a Cornish usually produces straight coats, because their recessive mutations are different and non-complementary.

Takeaway:Curly coats depend on matching recessive alleles — crossing gene types cancels the curl.

5. Hairless (hr/hr) — Sphynx-Type Mutation

Genotype:

• Hr- = Normal coat

• hr/hr = Hairless

Breeds influenced: Sphynx, some Peterbald lines via crosses.

Important note: Not all hairless cats share the same mutation — the Donskoy/Naked gene is dominant, proving that “hairless” is not one-size-fits-all.

6. Classic Tabby Pattern (tb/tb)

What it does: Turns a mackerel (striped) tabby into a blotched, swirling “classic” pattern.

Genotype:

• T- = Mackerel

• tb/tb = Classic tabby

Breeds where it matters: British Shorthair, American Shorthair, Maine Coon.

Why breeders care: Pattern clarity is a major showpoint in tabby breeds.

7. Chocolate (b/b) & Cinnamon (b1/b1)

Located at the B locus, separate from dilute.

Genotypes:

Genotype	Colour
B-	Black
b/b	Chocolate
b1/b1	Cinnamon

Breeds influenced: Burmese, Mandalay, Siamese/Oriental, British Shorthair, Tonkinese.

Key fact: You can have a chocolate cat (b/b) that is also dilute (dd) — producing lilac.

8. Amber (e/e) — Norwegian Forest Cat Exclusive

Genotype: e/e

What it does: Transforms black-based colours into warm amber tones over time — kittens often darken, then lighten dramatically as they mature.

Breed: Norwegian Forest Cat only.

10. Hidden Disease Genes

Not all recessive genes are desirable.

Some inherited disorders — such as certain metabolic diseases, enzyme deficiencies, and breed-specific conditions — are recessive.

That means:

✅ A cat can carry a harmful gene without any symptoms✅ Two carriers increase risk of affected kittens✅ Reduced diversity increases the chance of recessive diseases emerging. This is why DNA testing and diverse pairing are vital tools for modern breeders.

The Big Picture: Recessives and the Gene Pool

Selecting only for recessive traits — like only breeding dilute to dilute, or only pointed to pointed — leads to:

❌ Shrinking diversity

❌ Increased inbreeding

❌ Expression of hidden faults

❌ Greater disease risk

Recessive traits are beautiful — but diversity keeps a breed healthy.

Carriers help maintain that balance.

Key Takeaways

• Recessive genes shape many key breed traits

• Some recessives define entire breeds (Siamese, Rexes, Sphynx)

• Different recessive genes are not interchangeable

• Carriers protect the future of recessive traits

• Narrow breeding reduces diversity and increases risk

Recessive genes aren’t just colour modifiers — they’re part of the architecture of modern breeds.

Final Thought

Behind every pointed mask, curly coat, lilac shimmer, or hairless body lies a recessive story — preserved, carried, and passed forward by generations of thoughtful breeders.

Understanding these genes isn’t just fascinating — it’s essential to keeping our breeds resilient, diverse, and thriving.