An In-Depth Look with Dr. Ingrid Pyka
You may have heard of “doggy DNA” on the news, or discussed it with a friend at the dog park. Could canine DNA testing really reveal your loveable mutt’s true genetic dispositions?
While you might like the idea of figuring out whether your dog’s spots mean he’s part Dalmatian—or if that splotchy black tongue means he’s got a bit of Chow or Akita mixed in, current DNA technology has brought an incredible value into veterinary medicine, both in the diagnostic and preventive avenues.
What is DNA?
To understand the applications of DNA it is helpful to know “genetic anatomy”. DNA stands for deoxyribonucleic acid. It is the basic root to all genetics. DNA is made up of a long strand of proteins spiraling as a “double helical” chain. Nearly each cell of an organism holds the same DNA material inside its nucleus.
The proteins that make up the DNA are set in highly specific sequences, thus establishing the exact genetic code for the organism. Sets of proteins, called a gene, determine the entire or at least some part of a single trait. Having a gene for a characteristic does not necessarily mean it will be expressed. Genes can be recessive or dominant and even turned on and off.
Collectively, all the genes on the DNA strand are the genome. The genome is the unique genetic recipe to create and maintain that, and only that one organism.
The DNA further coils into strands called chromosomes. In most mammals, two chromosomes pair together, connecting either as a Y or an X shape. The Y chromosome establishes the male aspect of the animal.
Species vary in the number of chromosomes they have. Humans have 46 chromosomes (23 pairs), dogs carry 78 (39 pairs), and cats have 38 (19 pairs).
Using a small amount of blood or tissue sample, tests can determine the presence of DNA. Polymerase Chain Reaction (PCR) testing is just one test in a growing diagnostic field, in which a fragment of DNA is replicated to a detectable level. These various DNA fragments are the codes for specific genes of interest.
Since infectious agents, such as bacteria or viruses, contain DNA too, their genetic trails can also provide a diagnosis. As they replicate within the body system they infect, they produce an abundance of DNA in the host’s body. PCR tests are gaining increasing levels of accuracy in infectious diagnostics.
With either a small blood sample or a cheek swab, a DNA analysis can recognize the major genomes from most of the AKC breeds.
DNA Testing for Dog Breed Identification
Several companies now offer dog breed identification through DNA testing. With either a small blood sample or a cheek swab, a DNA analysis can recognize the major genomes from most of the AKC breeds.
DNA testing identifies only the strongest genes in the animal’s ancestry. Just like humans where a child may look just like one parent, but have little or no resemblance to the other, a mixed breed dog will also carry the DNA of both parents, but may not necessarily look like them. For pet owners simply curious as to their “mutt’s” heritage, mixed breed gene mapping may answer some questions, or bring some surprises.
Since many breeds have a predisposition to certain medical issues, identifying mixed breeds animals may provide important forewarning of potential problems. One mixed breed dog, for example, may be found to have collie, Labrador retriever, and Great Dane in its ancestry. Collies are known to have reactions to ivermectin, a commonly used antiparasitic medication. Labradors often have hip dysplasia, a crippling hip joint abnormality. Great Danes frequently develop osteosarcoma (bone cancer). Knowing each of these potential risks, the veterinarian may elect to prescribe this patient a different parasitic preventive that is safe for collies, encourage earlier use of dietary and supplementary treatment to prolong the hip health, and more aggressively diagnose and treat any lameness that occurs in this dog.
Labeling a Hereditary Gene
Just as a gene can signal a particular trait, a pathologic gene can also trigger the development of a birth defect or a disease process. Many such hereditary abnormalities have been identified and mapped in the DNA and an increasing number of tests have been devised to diagnose them.
Maine coon cats, for instance, too often develop hypertrophic cardiomyopathy (an enlarged heart). In another example, Doberman pinchers have a high incidence of von Willebrand’s disease (a blood clotting abnormality). Both of these conditions have been linked to specific genes. If a blood sample or cheek swab detects these mutant genes, your veterinarian may be more vigilant of your cat’s heart or your Doberman’s surgical risks.
Though the detection of a “bad” gene does not necessarily mean the animal will develop the malady, breeders may stop breeding the carrier to prevent the passing of that gene. If the gene is not found, however, any animal still has the potential of developing any of the medical issues. Carrying a particular gene merely indicates a higher chance that it may be expressed.
Canine DNA Registries
Being able to catalog and register DNA findings has become another way for breeders to strive for stronger and healthier lineage. In an attempt to minimize hereditary defects, many registries offer lists of breeding animals that do not carry a particular gene.
Some breeders use DNA identification as a source to prove the purebred status of their animal. Other people use the DNA to hold on file in case of the theft of their pet. The possibilities of DNA research are just beginning.
Running a Canine DNA Test
Usually all the laboratory needs is a tissue sample, such as a cheek swab, or a small amount of blood. Analyses can cost anywhere from $65 to $250 or more, depending on the test.
Many DNA tests do not require a veterinarian to submit the sample. However, a veterinarian may be a better guide for you as to which test to run and which laboratory to use. Working with a medical professional may also help you understand more of the valuable information regarding your pet that the results may provide.
Though many of the tests are run by independent laboratories, a large number have been developed at universities who are still continuing to gather data on the results they obtain. The continual research they run help the veterinary profession as a whole in determining the best prevention, diagnostic, and treatment plans.