Genetic testing your dogs: What you need to know

By Dr. Mikel Delgado, PhD

Genetic testing your dogs can be fun and informative, but are the tests reliable when applying results to your breeding program? And are there dangers in relying on genetic testing when making decisions about breeding?

What is a genetic test?

A genetic test (also known as a DNA test) identifies changes in chromosomes, genes or proteins which may be related to disease processes, physical traits, parentage or ancestry. DNA tests can examine regions of interest in an individual’s genome for those changes.

How does a genetic test work?

The first step of getting your dog tested is to send in a sample. This could be from blood, tissue, or a simple saliva or cheek swab. Once a laboratory receives the sample, the DNA is extracted. This is a process where a cell and its nucleus are broken open to release the DNA. The DNA is then prepared in a way that separates it from any debris from the cell, and then it is cleaned. 

Next, the DNA is copied and “amplified” during a process called polymer chain reaction (PCR). Think of PCR as a photocopier that will make it easier to see what is happening inside the DNA.

Each gene has a “code” of nucleotide sequences, which are the molecules that provide our bodies with “instructions” for building proteins.

Types of tests for your dog

After amplification, thousands of areas of the genome can be closely examined. One way to do so is genome sequencing, when the entire genome is detailed into its nucleotide sequence, providing an individual’s entire blueprint. Genomic sequencing is rapidly becoming more accessible, but it’s still not commercially available for dogs. 

Standard direct-to-consumer DNA tests instead focus on specific areas of the genome where mutations or variations are likely to exist. These areas, known as single nucleotide polymorphisms (or SNPs, pronounced “snips”) act as biological markers, helping scientists locate mutations in genes that are associated with a disease.

What can DNA tests tell you about your dog?

You got the test done - but what does it all mean?

The most important thing the test can tell you is if your dog carries a specific genetic variant in a region of concern. If so, they may be able to tell you if that variant is associated with a specific disease or condition in dogs or in your breed.

In many cases, your DNA results can help you make breeding decisions. For example, if you have a dog who is a carrier for a problematic condition, you do not want to breed them with another carrier, as that will increase the risk of having affected puppies. 

With recessive disorders, you may choose to breed a carrier to a non-carrier, which prevents you from having affected puppies. Ideally, you replace carriers with clear dogs in future generations. But responsible breeders accept that sometimes they must limit breeding choices based on test results to prevent the creation of dogs that will be affected by serious health problems.

Some genetic companies can also help by providing you with a COI (coefficient of inbreeding). You can test both dogs you intend to mate, and the COI gives you information about the risk of inbreeding and of passing on homozygous alleles for harmful mutations. Combined with information from your dog’s pedigree, this is a very effective way to make ethical and medically sound breeding decisions.

DNA Testing of Dogs: Limitations

DNA tests may seem magical but they can’t do everything.

DNA tests cannot test your dogs for conditions that have an unknown genetic cause, even if they are heritable. Sometimes there’s no single test for a condition because it is caused by multiple genes or because researchers have not yet identified which gene(s) are related to the condition.

Some conditions that are heritable (such as hip dysplasia) require other types of testing, such as assessments of x-rays or a physical examination by a veterinarian.

Genetic testing can be breed specific - it may not be necessary to do 120 genetic tests on your dogs if your breed is not at risk for 120 conditions, so don’t be oversold on the usefulness of genetic testing. Know its limitations.

Genetic testing is about probability. It cannot always definitively tell you whether an individual  dog will or will not develop a condition. DNA tests are also not sufficient to diagnose a health problem. But it can be helpful to discuss the results with your veterinarian or a genetic counselor so that you can learn more and make sound decisions for your program and dogs.

How to incorporate genetic testing into your dog breeding program

• First, check your breed club requirements, which are also available in the CHIC database.
• Keep in mind the pedigree and phenotypic tests - genetic testing is just one tool in your toolkit
• If you still have questions, you can make arrangements for a consultation with a veterinary genetics counselor
• You can also participate in ongoing research and register your test results to help advance our understanding of each breed’s health needs and concerns