PART TWO: Hidden Carriers — The Silent Powerhouses of Breeding

How recessive genes stay alive, disappear, and suddenly reappear in our cats

When a kitten is born, we immediately notice its phenotype — its visible traits (or "photo"): colour, coat, pattern, eye colour. But what we can’t see is just as important. Beneath every coat lies a genotype — the genetic code — and sometimes that code contains a hidden recessive gene that doesn’t show in the way the cat looks.

Those cats are called carriers, and they’re one of the most misunderstood — and most valuable — parts of breeding. Although we're talking about coat colours, this all applies to other genes as well and when you breed only with coat colours in mind, you will be dragging along the whole DNA as well and creating a lot of other recessive genes in your cats -some of these may be of no consequence but some may be undesireable.

What Is a Carrier?

A carrier is a cat that:

• Has one copy of a recessive gene

• Does not show the recessive trait

• Can pass it on to its kittens

For example, a cat with the genotype Dd carries dilute — but still looks full colour. The recessive allele d is there, but masked by the dominant D.

Genotype: What the genes are (the genetic code)

Phenotype: What we see (photo)

A carrier’s phenotype looks normal — but its genotype tells a different story.

Three Burmese kittens, a seal (carrying dilute dd) and a blue (dd) and a lilac which is the dilute of chocolate (dd)

How Recessive Genes Hide (and Surprise Us)

Recessive genes stay hidden because they need two matching copies to appear. This means a trait can skip:

• one generation

• five generations

• or even longer

All it takes is the right combination — two parents who both pass on the recessive allele.

That’s how a dilute kitten can pop up from two full-coloured parents, or a longhaired kitten from two shorthaired parents.

Why Carriers Matter in Breeding

Some breeders shy away from carriers — but genetically, that’s risky. Carriers:

• Keep recessive traits from disappearing

• Increase genetic diversity

• Prevent bottlenecks and colour loss

• Allow healthy lines to continue

• Support rare recessive traits (like lilac, fawn, or longhair)

Eliminating carriers entirely can accidentally eliminate the recessive gene itself — sometimes forever.

Carriers aren’t flawed. They’re genetic vaults.

The Risk of Only Breeding for Recessive Traits

While recessive traits can be beautiful and desirable, there is a real danger in breeding too narrowly for them.

When breeders focus only on producing recessive offspring — for example:

• Only dilute

• Only longhair

• Only pointed

• Only specific colour combinations

— the breeding pool becomes smaller and smaller and this isn't just the coat colour and type genes, it will also drag the other genes along with it due to the narrow breeding required.

Why that’s a problem:

Breeding only from a limited group of cats:

• Shrinks the gene pool

• Increases inbreeding

• Reduces genetic diversity

• Raises the risk of inherited problems

• Can expose hidden faulty recessive genes

Recessive traits don’t just apply to colour — some harmful conditions are recessive too. When diversity drops, the chance of two carriers of a harmful gene meeting increases, and disease can emerge unexpectedly.

In other words:

The more narrowly we select, the more genetic baggage we uncover.

Responsible breeding balances type, colour, health, and diversity.

When Do Carriers Matter in Planning a Mating?

Carriers become important when:

• You’re aiming for a recessive colour (e.g., dilute, chocolate, lilac, cinnamon, longhair)

• You want to preserve a recessive trait in the breed

• You’re working with a trait that’s rare or valuable

• DNA testing shows a hidden allele you didn’t expect

In all these cases, carriers give breeders options.

Punnett Square Example:

Carrier × Dilute (Dd × dd)

Let’s imagine a mating between:

• Parent 1: Full colour carrier of dilute (Dd)

• Parent 2: Dilute (dd)

Punnett Square

            Parent 2
              d      d
Parent 1  ----------------
     D     |   Dd   |  Dd  |
           ----------------
     d     |   dd   |  dd  |
           ----------------

Expected Outcomes

• 50% Dd — Full colour, carriers

• 50% dd — Dilute kittens

So half the litter will look dilute, and the other half will carry dilute.

🔹 The Danger of Losing Recessive Traits

If breeders only select cats that show the recessive trait (e.g., only dilute, only longhair), and never breed the carriers, eventually:

• The carrier pool shrinks

• Genetic diversity drops

• The recessive gene may vanish

Once a recessive gene is gone from a population, the only way to restore it may be:

• Outcrossing

• Using frozen semen from old lines

• Or accepting that the trait is lost

Carriers are insurance.

Ethical Use of Carriers

Carriers should be bred:

• Thoughtfully

• Transparently

• With health and type as priorities

A responsible breeder:

• Keeps good records

• DNA tests when useful

• Discloses carrier status honestly -especially when selling breeding cats

• Plans matings that avoid harmful recessive pairings (e.g., disease genes)

Carriers are not second choice — they’re strategic assets.

Key Takeaways

• Carriers hold recessive genes without showing them

• A recessive gene needs two copies to be expressed

• Carriers help preserve rare traits and diversity

• Carrier × carrier can produce recessive offspring

• Carrier × dilute produces 50% dilute

• Carriers are vital to the future of many breeds

Final Thoughts

Some of the most stunning colours and coats in cat breeding exist today because generations of carriers quietly protected them. Understanding — and valuing — carriers isn’t just smart breeding, it’s good stewardship of the breed.