What can a DNA test tell you about your dog’s breed status?

Genetic testing has radically shifted how we think about dog breeds; several commercially available tests offer an analysis of your dog’s ancestry. But purebred dogs existed long before genetic testing was available to every dog owner. 

How were dog breeds developed?

Although dogs have been domesticated for thousands of years, it’s only over the past 150 or so years that dog breeds were developed through intensified selection for specific physical and behavioral traits. From selective breeding came the 350+ dog breeds that we know and love today. These breeds differ in appearance and genetics. 

The American Kennel Club, founded in 1878, maintains documentation, often referred to as “stud books,” for each recognized breed. Stud books originally documented the pedigree of every dog in a breed, but later changed to only dogs who had produced offspring. 

A closed stud book means no “outside blood” or new genetic stock is introduced into the existing population. The idea is that this closed stud book will maintain the ‘purity’ of the population and the integrity and reliability of breed characteristics or type. Most breeds fully recognized by AKC have closed stud books. 

Newer or developing breeds working toward AKC recognition may have open stud books, meaning that dogs can be registered with the AKC even if their ancestors were not. These dogs can also enter the breeding population of the developing breed. 

What makes a dog purebred?

According to AKC, a dog is considered purebred if their “sire and dam are members of a recognized breed and the ancestry of a dog consists of the same breed over many generations.” Typically, the dog will have a documented pedigree in a stud book over many generations. 

A dog can be purebred and not have a pedigree – that means that the breeder may not have completed paperwork to register the dog. Dogs that will be bred, or will compete in some shows, typically need a pedigree and registration to prove their purebred status.

Although DNA testing may indicate that your dog is purebred, a DNA test is not sufficient to register a dog as purebred. An ancestry test compares parts (known as markers) of your dog’s genome (complete set of genes) with those from a database of other dogs with a known, registered pedigree. The test assesses how similar your dog’s DNA markers are to dogs of different breeds. The closer the match to a given breed, the more likely a dog is identified as that breed. 

Companies that specialize in canine genetic testing claim 95-99% accuracy at identifying ancestry, but they do not guarantee that they will correctly identify every dog’s breed or breeds. The more established a breed and the larger the population of dogs in the database, the less likely it is that a purebred dog would test as mixed breed. 

What if my dog’s DNA test says they are not purebred?

Unexpected results might occur when the identified breeds are closely related, or if the dog is from a subpopulation that is not well represented in the database (e.g. an imported dog). If you have a rare or newer breed, there may be less reliable genetic data available in the testing company’s database.

The best way to guarantee your dog is purebred is through:

• registration with a reputable national or international registry (such as the American Kennel Club, Canadian Kennel Club, United Kennel Club, Kennel Club, or the Fédération Cynologique Internationale) and/or a breed club AND
• paperwork demonstrating a multigenerational pedigree 

However, if your dog’s DNA test indicates your dog is mixed breed, and your dog is not registered with a multigenerational pedigree, it is possible that your dog is not purebred.

What do I look for when beginning my puppy search?

If you’re looking for a purebred puppy, look for one whose parents are registered with an organization that requires a multigenerational pedigree. Ask a potential breeder questions about their breeding dogs’ pedigree, what registry they are part of, and what records will be transferred to you when you bring your puppy home.  

References and resources

American Kennel Club: DNA And The AKC

Embark: Can a Registered Purebred Dog Appear as Mixed Breed on a DNA Test?

IAABC: How Accurate are Those Dog DNA Tests? Insights and Challenges in Decoding DNA

Michigan State University Animal Legal & Historical Center: Pet Purchaser Protection/Puppy "Lemon Laws"