Saturday, April 4, 2015

If You're Gonna Have An Opinion On Mixed VS Purebred Dog Health, Then You Need To Know The Basics Of Genetics

Over the past week, I have seen multiple comments that have bothered me something fierce.  At the core, it comes down to the simple fact that the general public doesn't know the basics of genetics, nor the modes of inheritance.  And where as it seems rather cruel to expect everyone to know the basics of the basics, these people can't even draw the some of the same conclusions by looking at their fellow human beings.  Which is truly odd, considering all the medical shows, both fictional and non. 

Hell, even when there is an article that talks about a certain genetic trait in humans, and how it is a dominant gene that only takes one parent, I have still seen people go on about inbreeding being the cause.  Reading is fundamental, sir.

My simple belief is, if you're going to have an opinion on something that has science behind it, know the damn science, even if it's just a little bit.  So, this is what I'll be talking about today. 

Dominant Gene:  Only one parent is needed to pass the trait/disease at a 50% chance, and only one copy of the gene is needed for expression.

This means, if you have a human with Huntington's or a Brittany Spaniel with Hereditary Canine Spinal Muscular Atrophy, it doesn't matter how unrelated the other parent is (same breed or not), there is always a 50% chance of any given offspring getting the disease. 

Recessive Gene:  Two copies of the gene is needed for expression.  If an animal or human only has one copy, it typically has no effect, and those with one copy are called "carriers".  A human or animal who is a carrier, can breed to a non carrier, and will produce non-carriers and carriers.  An affected human or animal with two copies of the gene, bred to a non carrier, will produce all carriers.  Two affected will produce all affected.  An affected with a carrier will produce 50/50 carrier/affected.  Two carriers will produce 25% affected.

If you have a Siberian Husky who carries Progressive Retinal Atrophy and breed it to an Irish Setter that also carries Progressive Retinal Atrophy, you have now produced a litter of carriers and 25% affected.  Congratulations, you have produced a genetic disease in the supposedly healthier "mix breed".

Polygenic Genes:  Multiple genes combination to produce a trait or disease.

If you have a German Shepherd with A and B parts of a 3 part code for a disease, like say, Hip Dysplasia, and you have some random Boxer mix who carries A and C....you're likely going to get some Boxer/GSD/? mixes with HD. 

Now, this is just a simplistic overview.  There's also Sex-linked genes, mitochondrial DNA, and other factors that we're still learning about. Genetics is a fairly young science.  Some health issues can even be caused.  But the basics give you a basic understanding of how and why things can go wrong with the health of mixed breeds, why mixed breeds don't magically get a pass with health.

Now, in theory, if two breeds had completely unrelated problems that were solely recessive, could a mixed breed between the two be healthier?  Possibly.  But you still have to take in another issue that isn't related to genetic diseases, but the genetics behind conformation-how a dog is put together. 

This area is tricky.  We can't map out everything in dogs, at least not yet.  However, consider two different head types.  Now, some of the discussion I've seen has people saying that the genes for the top jaw and lower are different sets.  So, if this is true, you could end up with a mouth in a crossbreed that is poorly put together and may cause the dog some issues, however minor.  When you look at the whole picture, every part of the dog, you could very well end up with a mishmash of conformation that may or may not cause the dog to break down physically as it ages.  Within an entire litter, there may be a wide variation of traits, and some may be fine, others may live a life of pain or discomfort from early on.  It's Russian Roulette with genes, especially as the majority of people breeding crosses on purpose seem to do no genetic testing (because "mixed breeds are healthier", so why bother?) and have little to no understanding of genetics in the first place. 

And we're not even touching on the subject of temperaments and drives, which....is one more very important factor in breeding.  

All in all, it's important to go to a breeder who knows their lines, health testings, does something with their dogs, and has an understanding of genetics.  Doesn't matter what breed, or even if it is a cross, it is.  This is how you stack the odds of health in your future dog's favor. 

But wait!  There's more!

I'm going to give a basic run down of some facts.....

-Health tests are available for some diseases.  However, the number of tests available vs genetic diseases out there is quite small, though ever growing. 

-Health tests are often breed specific/limited to a number of breeds, as even though a number of genes are the same across breeds, not all are.

-Health tests should NEVER be confused with "Vet Checked".  Health tests are DNA tests that look for markers, or specific testing to check body parts.  Vet Checked is just a vet going over a dog/puppy to see if it is healthy at that point in time, and is no guarantee of future health.  And sometimes, vets do misunderstand certain things that may be breed traits or common in development in a specific line-vets are fallible, do not make any rash decisions or get angry until you've talked to your breeder about the report.

-Health tests are not perfect, and because there are so few health tests compared to the number of diseases, there may still be something that pops up.  Always let your breeder know so they have all the information possible to prevent and/or study such issues.

-Breeders, like vets, are fallible.  If there really is a problem, approach with a clear and level head, try to have an idea of what you want to do regarding the problem, and ask what your options are.  Flies, honey, vinegar, you know?

-Be mindful of the fact that even the best breeders are not psychic, and sometimes new problems in a breed will pop up with little to no warning.  This is a fact of life.

-If ever you are angry about an unpredictable health problem with your pet, look to the world, look to your fellow humans.  We have a right ol' mess of our own with genetic diseases.  And you know what?  You can't directly blame purity, inbreeding, or linebreeding for the majority of it.  Unless if you want to blame nature for possibly squishing our gene pool a couple of times, if I recall what science suspects correctly?