Dogs

Why Genetic Testing in Dogs Matters


Cavalier King Charles spaniels are at risk for both dry eye and curly coat syndrome. By: Alexas_Fotos

It tickles at the back of my mind to one day test my dog’s DNA, just out of curiosity, you understand (mingled with pug and beagle, maybe a touch of monkey?).

There are even test kits on Amazon where you swab the dog’s cheek and send the sample back to the lab. But when I mentioned this to a friend, her response was, “Are you thinking of breeding from Pogs?”

This puzzled me, and it was only later I realized she was confusing genome tests for inherited disease with DNA tests for dog breed. This is an easy mistake to make, but it’s a bit like comparing a photograph to an MRI scan: one is deep and searching for disease risk, and the other is superficial, looking at appearances and breed.

Your Dog’s Breed

Perhaps, like me, you have a cross-breed dog — which is exactly what a hybrid or designer dog is. Like tracing your own family tree, it can be fascinating to work out your dog’s exact parentage and any interesting out-crosses lurking in recent generations.

But as well as satisfying your curiosity, it can be useful to know what breeds are beneath the fur. This can give you clues about what health problems to be vigilant for.

Certain breeds are linked to an increased risk of disease. For example, German shepherds suffer with skin allergies, while Labradors are prone to hip and elbow dysplasia. By knowing your cross-breed has some Labrador in them, you can decide whether or not to protect their joints with a food supplement to reduce the chance of them developing early arthritis.

Home Test Kits

Home DNA test kits can satisfy your curiosity without a trip to the vet. You can buy a variety from the internet. Simply search “dog DNA kits,” and you’ll see what I mean.

You’ll be sent a small kit containing a swab, transport medium and a short questionnaire to send back to the lab. Obtaining the sample couldn’t be simpler: You simple wipe over the inside of the dog’s cheek with the swab and then pop it into the given packaging.

The harvested sample of cheek cells is then sent to the lab for sequencing. They compare the DNA sample to a database for purebred dogs to look for the matches. The percentage of each parent breed is worked out and sent in a report.

A top tip is to select the lab with the largest database of reference breeds. This means if your dog has something unusual hiding in their DNA, the lab is better able to pinpoint it exactly rather than giving a close approximation.

Ailments like skin allergies and hip and elbow dysplasia are sometimes genetic in certain breeds. By: Bieniu94

Health Screening and Genetics

The other side of doggie DNA is screening for genes that carry or code for inherited diseases.

This is different from the home test kits mentioned above and usually involves a vet visit and a blood sample (this is changing, with some specific screening tests now available as cheek swabs). The blood is then sent to a specialist genome lab where coding on the DNA helix is examined for sequences that spell trouble.

Why Genomes Are Interesting

Many distressing diseases can be passed down from parent to pup. But some of these don’t develop until the parent dog is in middle or old age. Thus the dog produces the next generation before it’s realized they have the potential to pass on the problem.

It’s sobering to know currently there are around 350 inherited diseases that have been identified in dogs. That’s an awful lot of potential heartache right there, if it means your cute puppy has an incurable metabolic disease, leading to a shortened life.

Now imagine the breeder knowing ahead of breeding whether the dogs will produce a healthy generation or not. If the potential parent tests positive for passing on a debilitating health condition, in theory, the breeder simply won’t breed that dog.

If you have a dog who went blind from progressive retinal atrophy or suffered premature arthritis, this has got to be good news for your next pup. If everyone played by the rules, then certain genetic conditions could be gone in 1 or 2 generations.

Check out this interesting video about dog genetics:

Why Genome Projects Matter

A dog is made up of trillions of cells, each containing a nucleus. Take a giant magnifying glass to the nucleus and you’ll see it’s made up of 78 chromosomes, each composed of DNA (deoxynucleic acid).

Those DNA molecules code for the creation of the proteins that build and maintain the body. Get one of those DNA sequences wrong, and the body has an inherent weakness, a bit like a knitting pattern where the instructions incorrectly tell you to drop a stitch. Genome projects identify specific places on the chromosomes that code for specific traits. In other words, they proofread the knitting pattern to ensure it’s correct.

For inheritable diseases, canine genome tests check for errors or “misprints” on the DNA. When a parent dog is found to have a faulty genome, then not breeding from that dog (and choosing a healthy parent instead) will eradicate that genetic condition.

Genome sequencing can also help determine which health problems are linked to which breeds, which can help move forward knowledge about diagnosis and treatment.

Examples of breeds and diseases currently under the subject of research include:

  • Beagles and steroid-responsive meningitis
  • Border collies and idiopathic epilepsy
  • Boston terriers and premature cataracts
  • Cavalier King Charles spaniels and dry eye, curly coat syndrome
  • English springer spaniels and progressive retinal atrophy

There are far too many conditions under investigation to list.

Long story short, if you are thinking of getting a purebred puppy, then do some homework first. Find out what tests are currently available (search “[breed], genome tests”) to see what the options are. Then speak to the breeder to make sure their dogs are screened. The UC Davis Veterinary Genetics Laboratory is a good place to start.

All of which makes my simple curiosity as to how much pug/beagle/monkey is in Pogs seem a bit of an abuse of technology — but then again, it’s not so different from using the internet to watch funny cat videos.

References

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This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Feb. 2, 2018.



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