Understanding DNA Testing in Dogs: Direct, Causative, and Marker-Based Results

DNA testing has become an essential part of responsible dog breeding, but the terminology can be confusing—even for experienced breeders. Words like “carrier,” “at-risk,” “variant,” “causative mutation,” “linked marker,” and “risk allele” are used loosely in social media discussions, often leading to unnecessary panic or misunderstandings.

To help clarify the subject, this article breaks down the three main types of DNA test results you may encounter and what they truly mean for your dog, your breeding program, and your puppy families.

At Standard Poodles of Forest Lakes, we believe transparency and education are the foundation of ethical breeding. Understanding the science behind DNA testing is part of that commitment.

1. Direct (Causative) Mutation Tests

The gold standard. The mutation that causes the disease is known and validated.

These tests identify the actual genetic change responsible for a condition. They are the most reliable type of test available and are used across veterinary medicine, research, and responsible breeding.

Characteristics of Direct/Causative Tests:

• Mutation is scientifically validated

• The relationship between mutation → disease is well established

• Results follow predictable inheritance patterns

• Carriers will not develop the disease

• Clear dogs cannot pass on the mutation

• These tests are accepted by OFA, breed clubs, and veterinary geneticists

Examples in Standard Poodles:

• NEWS (Neonatal Encephalopathy with Seizures) – CLEAR evidence of causation

• vWD1 (Von Willebrand’s Disease Type 1)

• prcd-PRA

• CNM/EIC in Labradors (for comparison)

When the causative mutation is known, breeders can safely pair carriers to clears without producing affected puppies. Direct tests are extraordinarily powerful tools.

2. Indirect, Linked, or Marker-Based Tests

These do NOT test the mutation—only a piece of DNA close to it.

This is where confusion often arises.

A linked marker test identifies a genetic variant near the suspected disease-causing region, but not the mutation itself. These tests are often developed when:

• The true mutation hasn’t been discovered

• Research suggests an association, not a cause

• Disease expression varies by breed

• There are protective or modifier genes at work

Characteristics of Indirect/Marker Tests:

• Do not test the actual disease mutation

• Results may vary significantly by breed

• A dog can test “at-risk” and remain healthy for life

• Expression may require additional, unknown genetic factors

• False positives are possible, especially across breeds

Examples Often Discussed in Dogs:

• Degenerative Myelopathy (DM – SOD1 variant)

  • Not causative in most breeds; marker status ≠ diagnosis

• Some PRA variant panels that report “risk alleles”

• Certain epilepsy markers

In Standard Poodles, the SOD1 DM test is a perfect example:
Poodles can carry the variant and never show clinical disease.

Marker tests provide information—but they do not predict disease with certainty.

3. Predisposition or “Risk Variant” Tests

These show increased probability, not certainty.

These tests identify variants associated with higher incidence of a disease in a population. They are not tied to simple inheritance patterns and often involve complex genetics.

Characteristics:

• Variant increases statistical likelihood, not guaranteed outcome

• Many involve polygenic or multifactorial conditions

• Environment, age, and additional genes contribute

• More useful for population-level studies than individual predictions

Examples in Dogs:

• Certain cancers

• Autoimmune disease risk variants

• Some forms of epilepsy

• Hip dysplasia polygenic markers (limited predictive value)

Risk variants should be interpreted with caution, ideally with veterinary or geneticist guidance.

Why This Matters for Breeders

Understanding the type of DNA test you’re using is critical:

✔ Preventing Unnecessary Exclusion of Healthy Dogs

Not all variants require removal from the gene pool.
Too much selection pressure based on non-causative or low-impact variants can reduce genetic diversity—a far greater threat to breed health.

✔ Maintaining Realistic Communication With Puppy Buyers

Buyers often see “carrier” and panic unless the breeder explains inheritance.
Your education protects your reputation and your families’ peace of mind.

✔ Avoiding Overinterpreting Marker Tests

Treating marker variants like causative ones can lead to poor decisions and misinformation.

✔ Making Evidence-Based Breeding Decisions

Causative tests = actionable.
Marker tests = interpret with context.
Risk variants = one data point among many.

Where Standard Poodles Fit Into This

In Standard Poodles:

Direct/Causative Tests (Highly Actionable):

• NEWS

• vWD1

• prcd-PRA

• MH (line-dependent)

These tests guide clear breeding strategies and prevent affected litters entirely.

Marker-Based or Risk Tests (Interpret With Care):

• DM (SOD1) — not a reliable predictor in Poodles

• CDDY/IVDD — not traditional in the breed, used mainly to avoid crossbred contamination

• Some broad “genetic diversity“ panels — informative but not diagnostic

As a breeder, your responsibility is to understand which tests truly matter and which require nuance.

Are Breeders Using the Right Descriptors?

Often… no.

Here’s the correct terminology you can confidently use:

Causative mutation

→ The actual genetic change that directly causes disease.

Direct test

→ A DNA test that detects the causative mutation itself.

Linked marker / indirect marker

→ A nearby genetic variant used as a proxy when the real mutation is not known.

Risk allele / predisposition variant

→ A variant that increases statistical likelihood but is not deterministic.

At-risk

→ In direct tests: will develop the disease.
→ In marker tests: may never develop the disease at all.

Carrier

→ For direct tests: will not become affected but can pass the mutation.
→ For indirect tests: not always meaningful.

Correct descriptors prevent misinformation—and elevate your credibility as a scientifically literate breeder.

Final Thoughts: DNA Testing Is a Tool, Not a Crystal Ball

The more we understand the science behind DNA testing, the better equipped we are to safeguard our dogs, our breed, and our breeding programs.

• Direct tests give us certainty.

• Marker tests give us clues.

• Risk variants give us probabilities.

• Breeders give these tools meaning through thoughtful interpretation.

At SPFL, we use DNA testing not to create fear or eliminate dogs unnecessarily, but to make wise, balanced, evidence-based decisions that protect both our puppies and the future of the Standard Poodle.