Genetics
What Is a Clear, Carrier, or Affected Dog? Genetics for Puppy Buyers
When a breeder shows you DNA results, you'll see 'clear,' 'carrier,' and 'at risk.' Here's exactly what those mean — and why it matters for your puppy's future health.
August 12, 2024 · 7 min read
The Three Results You'll See on a Dog's DNA Report
Canine DNA health tests categorize dogs for each tested condition in one of three ways: Clear (also called Normal), Carrier, or At Risk (also called Affected). Understanding these designations is essential for any serious puppy buyer.
Clear (Normal)
A clear dog has zero copies of the disease-causing variant for a specific condition. A clear dog will never develop that condition regardless of what genes they inherit from their mate, and they cannot pass the variant to their offspring. This is the best possible result.
Carrier (Heterozygous)
A carrier dog has one copy of the disease-causing variant and one normal copy. For recessive diseases (the most common type), a carrier is completely healthy and will never develop the condition. However, a carrier can pass the variant to 50% of their offspring. This is important for breeding decisions — two carriers bred together have a 25% chance of producing at-risk puppies. A reputable breeder will never pair two carriers for the same condition.
Carrier × Clear = Safe: produces 50% carriers, 50% clear — no affected puppies possible. Carrier × Carrier = Risky: 25% affected, 50% carriers, 25% clear.
At Risk (Affected / Homozygous)
An at-risk dog carries two copies of the disease-causing variant and will develop the associated condition — either at birth, in puppyhood, or later in life depending on the disease. Responsible breeders do not breed at-risk dogs for most health conditions.
Which Conditions Matter Most for Common Breeds?
- Yorkshire Terriers: Progressive Retinal Atrophy (PRA), Degenerative Myelopathy, Congenital Hypothyroidism with Goiter
- Cavalier King Charles Spaniels: Episodic Falling, Dry Eye/Curly Coat Syndrome, Macrothrombocytopenia
- Toy Poodles: Progressive Rod-Cone Degeneration (prcd-PRA), Neonatal Encephalopathy, GM2 Gangliosidosis
- French Bulldogs: Hereditary Cataracts, Degenerative Myelopathy, Canine Multifocal Retinopathy
What to Ask a Breeder About Health Testing
- Are both parents tested? (Both must be — not just one)
- Can you show me the actual DNA report? (Not just a summary)
- Are both parents clear, or is one a carrier? If carrier, what is the other parent's status?
- For the condition the breed is known for — what are both parents' results?