What’s Your Mutt’s Story, Part 2: Decoding a Doggie DNA Test

First and foremost, let me stress — I am NOT a trained, degreed scientist. I’m a geek of all things scientific, an at-home-experimenter, a nerd of the highest order. So all that I put forth in this blog is stuffed I’ve grokked from my own investigations, and information I’ve learned from interviewing Dr. Angela Huges, the chief veterinary geneticist from Mars Vet.

The purpose of this post? Essentially, I want to hit-the-highlights of what makes “doggie-DNA” so cool, so that if you choose to pursue a DNA breed heritage test for your own pup, you’ll feel you essentially know what you’re getting into. Before we get into the actual Wisdom Panel test and how it works, I think it is important to define a few things (mostly because I wasn’t 100% sure myself, and I don’t want to throw around terms if I don’t really understand them).  Dr. Hughes is a geneticist, she studies genetics…and is a DNA expert.  In casual conversation, I’ve heard “genetics,” “DNA” “genes,” and even “chromosomes,” used interchangeably when discussing, for example, why a dog looks a certain way — but they are not the exact same thing.

the study of heredity and the variation of inherited characteristics — ever wonder why one pup in the litter is yellow and the rest are black — it’s all about genetics, baby.

DNA: deoxyribonucleic acid  (don’t ask me to pronounce it, ‘cuz I always blow it) — DNA is the genetic code that makes you uniquely you, makes a dog uniquely THAT dog.  It’s a long, ladder looking sequence of four bases : adenine (A), cytosine (C), guanine (G) and thymine (T). The specific sequence of millions of pairs of these bases decides how everything in your body (and your dog’s body) is gonna work. It’s a SUPER long chain of information about EVERYTHING that makes up you and there is a chain of it in almost every cell in the body! It’s essentially a long list of every type of doggie treat (yes, I’m setting up a metaphor) possible to make.

Gene: a distinct sequence of nucleotides (the A-C-G-T bases that make up DNA) forming part of a chromosome, the order of which determines the order of monomers in a polypeptide or nucleic acid molecule which a cell (or virus) may synthesize. Basically, it’s a specific segment of that long ladder of DNA that contains a specific recipe for a specific thing. Imagine DNA is every page of a cookbook of doggie treats, but the page for peanut butter molasses doggie cookies is a single gene.

Chromosome: a strand of DNA encoded with genes.  Every cell has 22 pairs of DNA chromosomes, plus two strands of sex chromosomes (that whole “XX” for females & “XY” for males thing).  Going back to the doggie treat metaphor, chromosomes are the neat & tidy recipe folders that you put all of the recipes into for easy access and efficient storage.

So…when I scrubbed Ullr’s cheek with the swab, it was gently scraping off a bunch of cells (that each contained a full ladder of DNA). The folks at the lab, then extracted the DNA, noted the sequence, which is called his to determine his genotype (his specific genetic make-up — see a snapshot of a segment of Ullr’s actual genotype below) and sent the sequence through an elaborate program (an algorithm) to compare his genotype to a database of over 12,000 pure breed samples (representing over 250 breeds). This program looks at all the different possible scenarios that could make up the last three generations of the dog, and comes up with their breed heritage tree (see Ullr’s genome segment below). From the Wisdom Panel website: “This process is called genotyping and is conducted on a canine Illumina® Infinium® chip created specifically for Wisdom Panel Canine DNA Tests. The chips are processed and analyzed at GeneSeek Laboratories in Lincoln, Nebraska.”

Screenshot from Ullr's DNA test results
Screenshot from Ullr’s DNA test results

After that analysis, they basically determine the dog’s genes — the specific segments that are the recipes for what makes him special. In my conversation with Dr. Hughes, she called these “markers” because they are in a known location in the chromosome and have been identified to result in specific traits, like size, or fur color, or ear shape, or…whatever. The test looks for over 1800 of these markers based on all that they know from the breed samples they have in their database. Also called “variations,” these markers don’t absolutely determine what your pup will look like, but they will outline the possibilities of his looks. Below is a graphic from Ullr’s test results that shows how different traits from different breeds might exhibit in a mixed breed dog:

Screen shot from Ullr's Wisdom Panel DNA Test
Screen shot from Ullr’s Wisdom Panel DNA Test

Some of the markers that might be noted in the dog’s trait might not jive with the way he actually looks, and several of the breeds that make up his heritage seem to have very little affect on his appearance (check out Part 3 of the Doggie DNA series when I unpack this aspect of Ullr’s test results).  I asked Dr. Hughes why there so often seems to be such a disconnect between the way a dog looks and the actual DNA:

“It’s important to keep in mind that physical appearance is really only determined by a relatively small number of genes. We know that the dog genome (the entire genetic code that is within a dog) is represented by about 3 billion base pairs…and within that, about 20 thousand genes…and out of that 20 thousand, only a very small number [15 or so testable variables] are impactful on what the dog actually looks like.”

So basically, your dog might have a ton of unseen aspects of a breed they contain, but have very few, if any, of the physical traits of that breed.  If I’m understanding Dr. Hughes — it’s about the testable traits — there may actually be genes in there that give even more information about physical traits — but DNA veterinary/canine science (which is a relatively new science) hasn’t yet discovered all there is to discover.

It’s really important to note that this doesn’t mean the science isn’t accurate (don’t be one of those people that discounts something just because it isn’t 100% finished and realized) — it just means that this science is still evolving, and will probably always be evolving:

“The future holds so much potential for genetics and our companion animals,” said Mars Veterinary Geneticist Dr. Angela Hughes. “At Mars Veterinary we’ve been working in the field of canine genetics for almost a decade and we’re now getting into feline DNA testing. As we move forward we see genetics as providing such a unique opportunity to explore proactive healthcare through advanced screening for all our companion animals—just like we can do for humans. We will continue to work with our research partners and the scientific community to do just this as well as expand our breed signature database and medical screening technology.”

Certainly, even in my own experience, I’ve seen the difference even 4.5 years can make in DNA science advances.  Tom Arnold, Ullr’s dog dad, did a DNA breed test about 4.5 years ago for Ullr, and other than showing a distant possibility of Chow-chow. The test we did this month was much more advanced and “felt” much more accurate. And with that in mind…hop on over to the next post to see those results!