Tag archives: dog DNA

In my last blog, I defined words that described when symptoms may present themselves in a dog affected with a genetic condition.  Today’s topic of discussion is how those symptoms show up (or not show up).  These terms are easily confused with each other.  I’ve even heard some geneticists can get these definitions mixed up.  Let me introduce two terms: Incomplete penetrance and variable expressivity.

Incomplete penetrance is a term that describes symptoms, which may or may not be present in a dog with an at-risk or affected genotype.  The dog has the mutated gene in the right number of copies to cause the disease, but the dog may not show physical symptoms of the disease.  As you can imagine, this can cause some confusion when examining the pedigrees of your dogs and this is when genetic testing becomes an important tool.  If genetic testing is positive, we know the dog has the mutation that causes the disease. Regardless if there are symptoms, this dog can pass this mutation on to its offspring.  Knowing this information may impact breeding practices, as discussed in previous blogs.  The concept of incomplete penetrance is an ...

My last two articles on dominant and recessive inheritance and X-linked inheritance have built upon each other and discussed different types of inheritance: dominant, recessive and X-linked.  These three modes of genetic transmission are fairly straightforward compared with the topic of today’s post, which is mitochondrial inheritance.  Maybe you’ve never heard of the word “mitochondria” before.  Or perhaps just reading the word brings you back to high school cell biology.  While this may be a rare form of inheritance, diagnosing a dog with a mitochondrial disorder may impact how breeders choose to breed their animals.

Before we discuss the mitochondrial inheritance, let’s talk about mitochondria. Just like our bodies need organs to function (kidneys, heart, liver, etc.), cells have organelles too.  One of the organelles is called a mitochondrion or mitochondria (plural).  Mitochondria are the energy powerhouses of the cell.  They create energy through a series of biochemical reactions.  The number of mitochondria can change depending on the type of cell (muscle, nerve, skin, etc.). 

The neat thing about mitochondria is that they have their own set of DNA, called mtDNA, separate from the DNA found in the nucleus; mtDNA is ...

The pointing Labrador is just one of many exceptional dog breeds. Versatile in their ability to point, flush and retrieve, pointing Labradors may be the perfect hunting companion.  How a specific dog breed has so many desirable characteristics is not a mystery. All domesticated dogs were bred for specific behavioral or physical traits that were required for certain jobs – whether it was for chasing and catching varmints, retrieving the evening’s dinner, or bringing in the herd, dogs are the perfect species for a variety of tasks.  

All of these traits, behavioral and physical, have a genetic component and are determined by an accumulation of genes with modifications, or mutations, that result in some outcome. Whether the traits are pointing, coat color or skull structure, humans chose founding stock to create the various breeds and bred these dogs for the traits they desired.  However, undesirable, even harmful genetic mutations were carried along in these breeds. The most ancient mutations can be found in many breeds of dogs, whereas those mutations that arose more recently maybe found in only one or two breeds.

With the advent of molecular genetic technologies and the sequencing of the domestic dog (Canis ...

My last blog talked about the basics of two types of inheritance for genetic conditions found in dogs: dominant and recessive.  To review, dominant conditions need one copy of the mutated gene in order for the dog to show symptoms.  Recessive conditions need both copies of the mutated gene inherited from each parent to have the disease.  Knowing the difference can change the way breeders choose which dogs to breed.  However, the wonderful world of genetics is not that simple.  Another pattern of inheritance is called X-linked, or sex-linked.  Although it is not as common as dominant and recessive; it is important to know which diseases follow this inheritance pattern, because it may impact breeding.

Dogs have 39 pairs of chromosomes (humans have 23).  Something dogs and humans have in common is the X and Y chromosomes determine gender.  XX is a female while XY is a male.  Females always give away an X chromosome to their offspring.  So, it is the male that determines gender for the next generation.  If he passes on the X chromosome, the offspring is female.  If he passes on the Y chromosome ...

Paw Print Genetics often gets asked about an optimal time to swab a new litter of puppies. When reviewing these tips, please keep in mind that it can take up to two weeks to obtain results once Paw Print Genetics has received the swabs.  Therefore, allow plenty of time for the laboratory to process your samples before promising a specific date that the puppy can join its new home.

Puppies and dogs can be tested at any age. However, it is a good idea to allow the puppies to stabilize after birth, bond with their mother, and demonstrate that they can feed and grow before testing.  You do not have to wait until the puppies are weaned; once the puppies are stable and thriving, they can be swabbed.  For puppies that are not weaned, the puppies should be separated from their mother for at least two hours prior to swabbing. This is to ensure we get the DNA of the puppy instead of the mom's DNA. During this time, they should have plenty of water and should not be allowed food to avoid contamination of samples. Once the swabbing is completed, the pups can rejoin their ...

On April 30th, you will be able to order genetic testing for your dogs from Paw Print Genetics^TM. Before we could open our doors for clinical testing, we had a lot of work to do, work that involved my entire family and our extraordinary staff.  We had to build an entire laboratory from the ground up. Part of that process was validating our tests, which, as I’ll explain, is an important and necessary step – and one that involved many of you. 

After more than 20 years of working in human genetic diagnostic testing, I decided to use these skills to improve genetic testing for inherited canine diseases. We are so grateful for the support of the community of dog owners and breeders who participated in our validation studies from December 2012 through March 2013. As unknowns in this industry, we appreciate your trust that we were doing the right thing with your dog’s DNA.

We set up our laboratory, designed our tests and conducted our validation as if Paw Print Genetics were a human diagnostic laboratory. This means that we have all of the validation documentation that would be required if we were regulated by ...

As a continuation of my last blog related to reasons that breeders give for not needing to do genetic testing, I felt that one of these deserved an entire blog of its own. Some breeders will say, "no problem has ever occurred in this family of dogs and I have been breeding this line for 20, 30, 40 years. I don't need to do genetic testing." From my perspective, these breeders either have not been looking very hard, aren't being particularly forthcoming, or denial is a wonderful thing (and a river in Egypt). When I started getting involved in what was referred to as a "very healthy breed" (per the people who had been breeding them for 20, 30, 40 years), I recognized 3 problems in my first 2 dogs that I would consider "genetic". I had not been told to look out for or ask about any of these issues in my extensive research on the health of the breed. In fact as I was at the breeder's home being told of this issue in my new puppy's mother and grandmother I was thinking, "Gee, that is a genetic problem that no one ever told ...

Many people with a "cute little dog" who are going to breed it to their friend's "cute little dog" and sell the puppies will say, "I don't need to do genetic testing on the dogs/parents, I am not a breeder." If you plan a litter of puppies, you are a breeder.

Other people will say, "There is nothing wrong with the mother and father, they are perfectly healthy. I do not need to do genetic testing." Carriers of genetic problems are often invisible and without testing; you cannot predict whether your litter will be at risk for disease.

Some people will say, "I am only breeding pets and I have never seen any issues in the puppies I produce. I do not need to do genetic testing." Pets are just as likely to get the genetic diseases associated with their breed as show or working dogs and in any scenario, people are quite obviously emotionally attached to their pets. $53.33 billion was spent in the US last year on pets with $13.67 billion of that spent on veterinary care alone (source). Many genetic issues do not get diagnosed as a genetic issue or may develop ...

Continuing the series on "when genes don't make sense," let’s talk about probabilities. Many people will hear that if a condition is recessive that one in four puppies will be affected or, if it is dominant, that 50% of the puppies will exhibit the trait or be affected with a condition. They will subsequently declare that because the outcome in their litter is different than these exact percentages, it therefore must not be… recessive, dominant or genetic at all.

On the other hand, many people in dogs will say things like "they need to breed a male in order to determine if he produces males or females."

These are different errors in reasoning relating to the same type of probability.

In the first case, people are expecting the actual results to be exactly what is predicted based on possible results or probabilities. In the second case, people are assigning meaning to the random variation that is usually observed (and actually expected) compared to what is predicted based on probability.

To start with the second scenario, millions of sperm are swimming as hard as they can to fertilize the eggs. Roughly 50% of these sperm carry an X chromosome ...