Author archives: Matt Tschirgi

Germline and Somatic Genetic Mutations in Dogs

Germline and Somatic Genetic Mutations in Dogs

My last blog discussed the complexity of inherited cancer predisposition syndromes.  A concept was introduced about the types of genetic mutations that can predispose a dog (or human) for cancer.  Some genetic mutations are passed through the blood line, while other genetic mutations are NOT passed on to the next generation.  Today, I would like to address this idea in greater detail.  These genetic mutations are called germline and somatic

Germline mutations are passed through the generations.  These are the mutations that show different modes of inheritance: dominant, recessive, X-linked, and mitochondrial.  Germline mutations are present in the sex cells (sperm and/or egg) and can affect multiple pups in a litter.  These are the mutations Paw Print Genetics offers testing for, which may impact breeding practices.  Breeders equipped with this information have the power to reduce, and maybe even eliminate, these mutations from breeding lines.  

Somatic mutations are genetic changes in the cells of the individual.  These mutations are usually not present at birth and can occur in any cell or organ over time.  These are usually due to environmental influences, although the exact triggers are often ...

The Importance of Testing for Adult-Onset Conditions in Your Dog

The Importance of Testing for Adult-Onset Conditions in Your Dog

An earlier article discussed congenital vs. adult onset conditions.  There seems to be some confusion as to the importance of the timing of disease symptoms.  I wanted to expand on the topic that we refer to as “age of onset”, or the age in which a condition starts to show symptoms.  Breeders may initially only be concerned with conditions that are congenital – present at birth.  While I agree that genetic screening for congenital disorders is important, screening for adult-onset conditions is also important, and should not be ignored.

Testing for congenital genetic conditions is probably a “no-brainer” for most breeders.  Genetic testing gives someone the knowledge to selectively breed dogs in order to reduce (or even eliminate) genetic diseases in the newborn pup.  As you may already know, breeding takes time and considerable resources.  Most breeders are also emotionally invested in the dogs they breed.  For many, it’s not just a hobby; it may be a full-time job or even a way of life.  Congenital diseases may cause a lot of discomfort to the affected pup, and can cause anxiety for everyone involved.  The cost of medical care may ...

Inherited Cancers in Dogs

Inherited Cancers in Dogs

In the world of human genetics, stories related to hereditary cancer predisposition syndromes have recently made quite a splash in the media.  For example, actress Angelina Jolie made a very public decision to have a double mastectomy in order to reduce her breast cancer risk.  There are other popular stories as well.  Although hereditary cancer predisposition syndromes are not as common in the canine population as they are in the human population, knowing a little information about these genetic conditions and how they work may impact breeding practices

What exactly is a hereditary cancer predisposition syndrome?  Those are a lot of complicated words.  Let’s dissect that phrase: 

                  Hereditary – inherited, genetic, passed from parent to offspring. 

                  Cancer – uncontrolled invasive abnormal cell growth. 

                  Predisposition – tendency towards or gravitation to. 

                  Syndrome – a group of symptoms with a single cause.

A hereditary cancer predisposition syndrome gives the affected individual a tendency to develop cancer.  Cancer, for the most part, is multifactorial.  That means there are genetic and environmental influences.  However, hereditary cancer predisposition syndromes have a much greater genetic influence than environmental influence ...

The Complexity of the Canine Genome

The Complexity of the Canine Genome

Genetic testing may seem simple on the surface.  Order a test.  If it’s positive, the dog will have symptoms.  If it’s negative, there is no risk for the disease.  Open and shut.  However, there are many molecular details that can make genetic testing extremely complicated.  Today’s topic is reviewing these facts and how they impact the diagnosis of a genetic condition and the chance it may happen again.  My goal isn’t to bestow upon you an honorary degree in genetics, but to help you understand how these diseases are diagnosed and how genetic testing for those diseases is designed and interpreted.

Although genetic testing is expanding at an extremely fast pace, it is not perfect.  Genetic testing can allow you eliminate certain conditions but, unfortunately, nobody has a crystal ball and can therefore, not exclude all possible diseases in any dog. Genetic tests are designed after a mutation causing a disease has been described in the medical literature. It may be a mutation common in a particular breed or it may be very rare. In addition, it may not be the only mutation in that gene, or there may be other genes ...

The Variability of Certain Canine Diseases

The Variability of Certain Canine Diseases

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 ...

Who’s on First: Congenital, Adult-Onset, and Progressive Conditions


When it comes to diagnosing genetic conditions in dogs (or in humans), doctors use a variety of clues.  One of those clues may not necessarily be what the physical symptoms are, but when did the physical symptoms start happening.  Today’s blog focuses on the when, not the what, of genetic diseases.  Although the when of genetic disease does not exclude the importance of what; when will be today’s topic.  Now that I’ve thoroughly confused you and you may be thinking about the old slapstick comedy routine “Who’s on First” by Abbot and Costello, let’s get started. 

“Congenital” is a term that often floats around the medical community when discussing disease symptoms.  It simply means “present at birth”.  This complicated word comes from the Latin root “congenitus”, which literally means “born together with”.  Con – with; genitus – to bear, or beget.  If a symptom or group of symptoms is seen right when a pup is born, it is congenital.  When making a diagnosis of an inherited genetic condition, knowing the symptoms are congenital can shorten the list of what genetic condition may be the cause.  Only recently has canine ...

Mitochondrial Inheritance is Responsible for Canine Disease

Mitochondrial Inheritance is Responsible for Canine Disease

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 ...

Beyond Dominant and Recessive: X-Linked Canine Inheritance

Beyond Dominant and Recessive:  X-Linked Canine Inheritance

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 ...

Genetics 101: Dominant and recessive traits in your dogs

Genetics 101: Dominant and recessive traits in your dogs

The field of genetics has progressed rapidly in recent years.  Perhaps you’ve seen headlines about these top genetic topics in 2013. These stories show the importance of genetics and how it affects us as individuals and as a society.  To understand the impact, though, one may need a review of Genetics 101: dominant vs. recessive disease traits.

In order for our bodies to work properly, our DNA must be coded in specific sequences.  DNA sequences are grouped into units called genes, which tell our bodies what to make to build cells and metabolize nutrients.  We are all a unique combination of re-shuffled genes from previous generations.  Everything from eye, hair and skin color, muscle, bone, etc. is coded by genes.  A mutation in a gene usually causes something to change and many of these changes can lead to disease. There are thousands of genes, and in humans, thousands of genetic disorders that result from mutations. 

One way to classify genetic disorders is to group them by how they are inherited.  With the exception of the sex chromosomes, X and Y, each of us has two copies of our genes.  One comes from ...