Monogenic vs Polygenic Traits in Dogs — What Every Puppy Owner Should Know

When we talk about genetics in dog breeding, most people imagine a simple “yes or no” answer — a dog either has a gene or it doesn’t. But in reality, not all traits or health conditions are controlled the same way. Some follow very clear genetic rules, and others are influenced by many subtle factors all working together.

Understanding the difference between monogenic and polygenic traits helps explain why some conditions can be tested for with high accuracy… while others require thoughtful breeding, monitoring, and long-term selection.

Let’s break it down simply.

🌱 What Are Monogenic Traits?

A monogenic trait is caused by a single gene. This means:

• The inheritance pattern is predictable.

• DNA tests can identify whether a dog is clear, a carrier, or affected.

• Breeders can make straightforward breeding decisions.

Examples of monogenic conditions in Cavaliers:

• Episodic Falling Syndrome (EFS)

• Curly Coat Dry Eye Syndrome (CC/DE)

• Degenerative Myelopathy (DM) (in most breeds — though its expression varies)

• Coat colour genes (like Blenheim, parti, tan points)

With monogenic traits, responsible breeders test, pair wisely, and avoid producing affected puppies. This is why DNA panels are so valuable — they tell us exactly what’s happening with these single-gene traits.

🌿 What Are Polygenic Traits?

A polygenic trait is influenced by many genes, each contributing a small amount. Unlike monogenic conditions, there is no single “yes/no” gene to test for.

This means:

• There is no accurate DNA test for these conditions.

• Risk is based on heritability, family history, and long-term selection.

• Expression is influenced by genetics and environment.

Common polygenic traits include:

• Mitral Valve Disease (MVD)

• Chiari-like Malformation & Syringomyelia (CM/SM)

• Hip and patella structure

• Temperament

• Longevity

These traits are complex — a dog may come from excellent lines and still develop an issue, or may remain clear for life due to the interplay of multiple genes and lifestyle factors.

🌸 Why This Matters to Puppy Buyers

When a breeder says “the parents are health tested,” it can mean different things.

For monogenic conditions:

You can be confident the breeder has eliminated the risk of producing affected puppies by:

• Testing parents

• Choosing genetically compatible pairings

• Ensuring puppies cannot inherit the disease

For polygenic conditions:

A breeder’s job is much broader:

• Long-term selection for heart-clear dogs

• Tracking relatives and lines

• Monitoring their dogs as they age

• Choosing mates that strengthen weak areas

There is no “one test fixes everything” — responsible breeding is a lifelong commitment.

🌟 The Sielle Place Cavaliers Approach

At Sielle Place, we pride ourselves on covering both sides of genetics:

For monogenic conditions:

Full Orivet DNA panels✔ Clear-to-clear or clear-to-carrier pairings✔ Zero risk of producing affected puppies

For polygenic conditions:

✔ Annual heart exams✔ Generational tracking✔ Selecting heart-healthy, sound, stable lines✔ Breeding mature dogs once we know more about their long-term health

This is why puppies from us come from parents who aren’t just “tested,” but purposefully and thoughtfully bred with the breed’s future in mind.

🐾 Final Thoughts

Monogenic traits are simple. Polygenic traits are complex. A responsible breeder understands both.

DNA testing is incredibly important — but it’s only one piece of the puzzle. Long-term health, structure, temperament, and soundness come from years of careful decisions, honest evaluation, and a commitment to the breed.