Dog and Cat Genetics: Everything You Need to Know

By Monica Weymouth

As pet parents, we like to think that we know everything about our companions. We know exactly where to scratch our pup’s ears and exactly where to look when sneakers go missing. We make sure kitty’s preferred windowsill is clear for afternoon naps and we would never dream of switching up her favorite dinner.

But how much do we really know about what makes our pets, well, our pets? Understanding our cats’ and dogs’ DNA can not only help us understand their endearing quirks, but it can also help us raise happy, healthy BFFs.

Pet DNA, Now and Then

It’s been around 10,000 years (and maybe as long as 30,000 years, according to some) since man met his proverbial best friend and thousands of years since cats and humans first cuddled up. Even so, on a molecular level, our modern-day pets are still surprisingly similar to their wild counterparts. A 2013 study showed that your lap cat shares 95.6 percent of its DNA with a tiger—something to keep in mind the next time kitty is stalking through the house. Canines, as it turns out, are even more closely related to their wild cousins.

“Evolutionarily, domestic dogs are closer to wolves and coyotes than domestic cats are to the great cats—tigers, lions, leopards and cheetahs,” says Jerold Bell, DVM, professor of clinical genetics at Tufts University. “Dogs can reproduce and produce living offspring with their wild cousins, while cats are too distantly related to be able to reproduce with the great cats.”

However, while wolf-dogs and coy-dogs may be possible, don’t start looking for one to bring home—when it comes to DNA, a percentage point or two is significant. Illegal to own as pets in many states, these hybrids pose significant behavioral and health challenges and are frequently turned over to shelters and sanctuaries.

Nature Versus Nurture

When was the last time you saw a Jack Russell lounge his way through a Saturday? Or a Shih Tzu get his precious little paws dirty? It’s no coincidence that breeds tend to share some predispositions, as genetics play a large role in the personality of our pets.  

“Different dog breeds were developed based on ancient behaviors of hunting, guarding, hearing, scenting and protection, and have different innate and inherited behaviors,” explains Bell. “Research confirms the notion that calico and tortoiseshell cats can have a more ‘fiery’ temperament. This can show as a greater propensity to hiss, chase, or lash out.”

With this in mind, it’s important to do some breed research before adding another member to your family—a puppy training class won’t necessarily overrule innate instincts.

“The power of genetics in determining canine temperament is particularly obvious in working breeds, such as the Border Collie,” says Casey Carl, DVM, associate medical director of Paw Print Genetics. “For hundreds of years, humans have selected Border Collies with the best herding skills to be the breeding stock for future generations. This has led to the creation of a profoundly intelligent breed in which puppies, sometimes as young as two or three months old, begin showing early signs of herding behavior without any training.” And while this herding behavior is highly desirable on the farm, it may prove less so if you live in a small, urban apartment.

While genetics has a hand in many tendencies, pet parents also play a large role. “Like humans, the temperaments of dogs are heavily influenced by both genetic and environmental factors,” adds Carl. “Though each dog is born with certain behavioral genetic predispositions, life experiences, particularly early life experiences, play a very important role in how these predispositions end up manifesting in the adult dog.”

Coats of Many Colors

What’s the difference between a tabby cat and a ginger kitty? Or a yellow lab and a black? In a word, genes.

With dogs, many breeders test their breeding stock for genetically determined coat characteristics to produce puppies with desired qualities, from curly blond locks to sleek brunette tresses.

According to Carl, there are at least four genes that determine color and over a dozen different genetic mutations that have been associated with the patterns, hair length, hair curl, texture and even shedding characteristics. “In addition,” he said, “it is suspected that there are still many undiscovered genetic mutations which contribute to the coat characteristics we have selected for.”

Curious as to where your cat got his good looks? Tests are also available to determine the genes at play in feline coat colors and patterns.

 

The Role of Genes in Illness

Genetics are also behind many of our pets’ illnesses. In dogs, common genetic-influenced diseases include allergies, hip dysplasia, heart disease, eye disorders, slipping kneecaps and some cancers. In cats, these include idiopathic cystitis (a type of feline bladder disease), diabetes, allergies, heart disease, cystic kidney disease, eye disorders and certain cancers.

With this in mind, if you are planning to breed your pet, it is imperative to perform DNA tests on both parents to increase the odds that the offspring will be healthy. A range of testing options are available—from simple cheek swabs to blood samples—and pet parents should work with their veterinarians to decide which tests are appropriate and necessary.

“It is not ethical to breed dogs and cats without selection of healthy breeding stock,” stresses Bell. “It doesn’t matter whether someone only breeds one litter in their lifetime or is a commercial breeder. It is not acceptable to blindly produce preventable genetic diseases that will cause pain and suffering to the animals and their owners.”
 

If you are purchasing a new pet, you can also do your part to encourage responsible breeding. Bell recommends asking for official documentation of health testing of the parents, and not settling for less.

“Some breeders will give excuses and say that their dogs or cats are healthy and don’t need testing, that testing is expensive, or that they offer a health guarantee,” he says. “A health guarantee that will replace your family member with another puppy or kitten if they develop a genetic disease is not an acceptable alternative to preventing disease.”

Raising Happy, Healthy Pets

Understanding the history and potential health problems of your pet’s breed can help you make smart choices when it comes to training and healthcare, and genetic testing can provide valuable information.

“For instance, testing a dog for blood clotting disorders or disorders of drug metabolism can determine if your dog may be at risk of life threatening complications during surgery,” Carl says. “Knowledge that a dog is affected allows owners to make informed decisions about what activities might need to be avoided in an effort to keep their dog happy and healthy.”

The bottom line: no one knows your pet better than you, but there’s still lots to learn. And when it comes to your best friend, the more you know, the better.