For each test, you have the possibility of receiving the following results: zero, one, or two copies of a variant. This will be displayed at the top of the result’s page in words and as a diagram of a double helix (DNA).
The likelihood of your dog expressing the disease depends on the mode of inheritance (MOI) of that variant as described below and the penetrance of the variant. The impact of the variant is also influenced by your dog’s breed(s), sometimes referred to as their genetic background. We recommend speaking with your veterinarian to discuss your dog’s results and clinical risk.
Modes of Inheritance
For diseases that are inherited in an autosomal recessive fashion, it means your dog is thought to need two copies of the variant to potentially express clinical signs.
For diseases expressed in a dominant manner, only one copy of the variant is needed for a dog to potentially express clinical signs.
Codominant and additive in general are used to describe variants in which dogs with one copy of the variant have a different phenotype from dogs with zero or two copies of the variant (although there is a slight difference between the two terms which goes beyond the scope of this article).
For diseases that are X-linked (the variant resides on the X chromosome), male dogs need just one copy of the variant to possibly be clinically affected—as they have only one X chromosome. For recessively inherited X-linked conditions, female dogs require two copies of the variant to possibly be clinically affected. Female dogs who have one copy of a recessively inherited X-linked variant are often referred to as carriers, but they can exhibit signs of disease that range from clinically asymptomatic to fully affected. This is due to a phenomenon known as X-Chromosome Inactivation.
Dogs with one copy of the variant will pass the variant to about half of their offspring. Therefore, if you plan to breed a dog with one copy of a breed-applicable variant, testing any potential mates and properly applying those results to your breeding program is recommended.
Dogs with two copies of the variant will pass the variant to all of their offspring. Therefore, if you plan to breed a dog with two copies of a breed-applicable variant, testing any potential mates and properly applying those results to your breeding program is of great importance.
Depending on the health condition and how many copies your dog has inherited, you may not have to remove them from your breeding program. You can learn more about incorporating carrier and at-risk dogs in your breeding program by reading Should I breed a dog tested as a carrier or at-risk?.
And, to learn more about what makes a health condition breed relevant, visit: What makes a health condition breed relevant?
Want to learn more?
To learn more about genetic terminology and breed, visit: In the Health Section, what does it mean for my dog if he or she has zero, one, or two copies of a variant?
To learn how to use your dog’s variant results to predict potential litter outcomes visit: How do I create Punnett squares and use them to predict litter outcomes?
And, if you have questions about the penetrance or clinical impact of a specific variant, you can learn more within your dog’s profile results, by reading the linked primary literature, speaking with your veterinarian, or contacting us