Genetic Testing

By MK9S

November 15, 2020

I have been very hesitant to make this post, but a few things have led to me deciding to actually do it. One major reason being, that I feel as though it is good information, and thought-provoking ideals that people should know in regards to genetic testing breeding stock.


I see so many people beginning to DNA test their breeding stock, or just personal dogs in general. I think this is an amazing thing, however what is not amazing is there appears to be quite a lot of misinterpretation surrounding this new craze, as far as what it means and what it does not mean. I find this to be a problem. In the age of mass amounts of information at our finger tips, people seem to either not care to find the education they need, or they simply don’t understand how to use it. DNA testing is quite an amazing technological advancement, but it requires understanding behind what that information means.


A very strong, and easy to use example is that of DCM (Dilated Cardiomyopathy). I imagine most “dog people” have heard of DCM or have at least a decent understanding of what it is. However, what I see time and time again is people do not realize what DCM in a genetic test “means”. DCM has this fun little thing, called incomplete penetrance and variable expression. Now in short, and a very very simplified explanation of that, means that a dog who is a carrier of DCM could be affected or not, a dog with two copies could also be affected or not, and even a dog with no “genetic abnormality” could be affected or not. Now there could be numerous reasons and causes for this, most notably one could argue we simply have not identified all genetic components associated with the disease, however, another argument could also be that there is an environmental aspect to the disease to cause it to become “active.”


Through this example, we can understand a very strong reasoning to understand what ACTUALLY our genetic testing means within our breeding stock. Of course, eliminating carriers from a gene pool is negligent, but in cases such as DCM, is it even wise to eliminate a “leader” from the gene pool? Dogs who are considered “leaders” of DCM of a certain mutation, can possibly never become affected by the disease. If you do your heart tests and the dog shows healthy, is it wise to lessen the gene pool with removal of that dog? These are of course, hypothetical questions that a breeder would have to ask themselves given their situation.


Now to extrapolate even further from this, in a study of Dobermans in Europe where they identified a few genes which seemed to have a linkage to DCM, they did the same study on Dobermans within the United States. Strangely enough, they found that the genes associated with DCM in European Dobermans did not have the same association with DCM in American Dobermans. Now of course, its different populations so is it really surprising? But in essence it brings up a very strong point, that genetics can be highly variable between different populations as well as breeds. And can also vary in the mode of inheritance.


To continue, having a clear dog through genetic testing does not mean that dog will never be affected by any disease, sometimes even diseases it was “tested for”. Genetic tests essentially show you what your dog is and isn’t a carrier or leader of within those specific genes that are currently identifiable with association to that disease. Also, those specific genes that, that specific lab tests for. So for example, a dog tested through Embark, you could say, My dog is currently clear for genetic markers of disease that Embark currently tests for/can identify. Now this is an important distinction, as in 10 years we can identify more markers, or in 10 years we may say, hey we were wrong about this marker. This does not mean that genetic testing is a crap shoot or not accurate. It just requires some understanding of what the information means and what it is telling you. It requires using thought and intelligence to further making better decisions within breeding and not just throwing out the baby with the bathwater.


Another point that seems to be missed. Every testing lab allows for a certain percentage/amount of error. Now this comes into play for numerous reasons, a big reason being that sometimes in genetic tests things come back where they weren’t able to “type” a certain allele or they weren’t able to really identify certain genetic markers. I know from personal experience of using Embark, that I have had dogs come back with 3 genes, sometimes, that they weren’t able to type/identify. In these instances, you can specifically request to have them “hand type” those markers to see if they can identify appropriately. This may not seem like a problem to some, but it actually is. If you don’t actually have the knowledge to read through the actual data of these genetic test and ensure that everything was typed/identified, there could even be genetic abnormalities common within your breed that could be missed. But you will never know, because you didn’t actually check the data. Further, people can also make mistakes in typing. No one wants to acknowledge this possibility, as we all like to live in the land of rainbows and unicorns where all is perfect. But in reality, it does happen. Labs even change their modes of testing due to large percentage of errors sometimes. Now once again, I am in no way saying genetic testing means nothing, I am simply saying, you need to know what the information is telling you and don’t make rash decisions from an uneducated perspective.


Next, different testing labs, also sometimes test for different genetic markers. I know Jeanette Mud did some research in regards to different labs and what different markers they test for. She wrote a nice article on her website in regards to this, so I won’t rehash what she has already written up. Here is a link to the article: https://www.jmpolicedogs.com/caninegenetics...


In the end, genetic testing is powerful information, but only to those who know how to wield it.