The Paw Print Genetics Blog

What To Test? - Selecting Sample Types for Genetic Testing

What To Test? - Selecting Sample Types for Genetic Testing

With canine genetic disease testing becoming an increasingly common practice in both pets and breeding dogs, more and more veterinarians are being tasked with assisting their clients with sample collection for genetic testing. Paw Print Genetics (PPG) accepts a large variety of sample types that can be used for DNA extraction. In some cases, certain sample types may be much more convenient or logical to submit for testing than others.


Cheek Swabs

While many genetic testing laboratories struggle with the small amounts of DNA obtained from cheek cells, the genetic testing at PPG has been optimized on DNA extracted from cells obtained from cheek swabs. After an order for testing is placed at, PPG will send an individually labelled, cheek swabbing kit (containing three cytobrushes) to the person placing the order for each dog being tested (unless the client intends to submit a different sample type and skips shipping during checkout).

In some circumstances, a client will opt to submit their own swabs of various types for testing. Though we accept the majority of swab types available, there are some that are better suited for cheek cell collection than others. In general, we recommend sterile brush-type swabs (such as those intended for cytology) over cotton swabs due to the increased surface area and subsequently increased DNA yields obtained from this type of swab. Swabs housed in any kind of culture or gel transport media are not compatible with genetic testing at PPG. Examples of brush-tipped swabs are provided on our website.


Dewclaws and Docked Tails

In an effort to meet breed standards, some clients routinely bring new litters to their veterinarian within the first week after whelping for dewclaw removal or tail docking. Removed dewclaws and tails make great samples for DNA extraction if removed and stored appropriately until submitted to the PPG laboratory. Given that these potential samples will provide large quantities of DNA and would typically be disposed of otherwise; dewclaws or tails may be preferable to collection of other sample types on a young dog. Having the option of submitting these sample types very early in a puppy’s life ensures that dog breeders will receive their results long before 8 weeks of age when they often plan to get the puppies to their new families.

In order to be used for genetic testing, simple collection guidelines should be followed to prevent contamination. Scissors, scalpels, forceps, or other instrumentation used in the removal of the appendages should be either thoroughly cleaned or exchanged for sterile instruments between each puppy. This is crucial in preventing DNA contamination between multiple dogs. Once removed, the appendage should be placed in a location labelled for that particular puppy such that they do not get mixed up with those of another puppy. These appendages should then be air dried in a secure location for at least a week prior to laboratory submission. Drying helps prevent DNA-damaging decay which frequently occurs during transit of freshly removed dewclaws or tails.


Umbilical Cords

If participating in the whelping or surgical removal of puppies, it is also possible for the laboratory to extract DNA from the puppies’ umbilical cords for genetic testing. Similar methods for instrument cleaning and tissue drying used for dewclaws or tails should also be implemented for umbilical cords.

Immediately after the cord has been clamped and cut from the puppy, a ½ inch section of the cord still attached to the placenta should be removed for drying. In order to prevent DNA contamination from the mother, it is also important to ensure that the mother has not licked or chewed the cord prior to sample collection.



Another common sample type used for genetic testing is semen. Though typically considered precious to breeders, in some circumstances, frozen or chilled semen may be the best sample to consider for genetic testing. This is particularly true in circumstances where a male dog is either deceased or unavailable to a person that has possession of the dog’s semen that they would like to use for insemination.

In general, approximately half of a semen straw or 3 to 4 frozen semen pellets are required to perform genetic testing at PPG. Though it is not required that the semen stay frozen during transit, it is recommended that semen is sent overnight to the PPG laboratory on ice packs in an insulated container to keep the sample cool.


Whole Blood and Blood Spots

Due to the ease of collection, outside of cheek swabs, one of the more common sample types submitted by veterinarians for genetic testing is whole blood. Whole blood should be collected in a lavender top (EDTA) tube. Like semen, blood should be submitted overnight, in an insulated container with ice packs in order to keep the sample chilled until delivery.

Blood collected on a filter paper card specifically designed for DNA capture such as Whatman FTA blood cards is also acceptable for testing at PPG. Blood can be expelled onto the card per manufacturer instructions. After drying at room temperature, the card will be ready for submission.  If blood cards are not available, we can also accept 2-3 cotton-tipped swabs soaked in blood and dried prior to submission.


Postmortem Tissues

Occasionally PPG has inquiries about testing tissue from a recently deceased animal for diagnosis of an inherited disease. Though the information obtained from this testing cannot be used to treat the dog in these circumstances, often times obtaining a diagnosis is crucial for the dog’s owner (and perhaps the veterinarian) to find peace with their recent loss. Nearly any tissue from the deceased dog can be submitted for testing. However, if a necropsy or postmortem exam is performed on the dog, samples of skeletal muscle, heart, kidney, or liver would be preferred. However, if no postmortem examination is performed, a section of tongue is a commonly used, easily accessible tissue for testing.

Samples collected for testing should be from dogs that have been deceased for fewer than 3 days. If not shipped immediately, tissues should be stored at -20oC until shipped. Tissue samples can be placed in a sterile container such as a red top collection tube or Whirl-Pak bag for shipping. As with blood and semen, postmortem tissues should be sent in an insulated container with ice packs to prevent decay.


Contact Us

For more information about collection or submission of any of the sample types described above, simply click on any of the section headers to link to the PPG website. If you have questions about a specific sample type, setting up an account for your veterinary practice, or if you have any other questions about genetic disease or trait testing through Paw Print Genetics, please contact the laboratory at or call to speak to our knowledgeable staff at 509-483-5950 (Mon. through Fri.; 8 am to 5 pm Pacific time).

*Photo courtesy Austin Community College via Flickr Creative Commons license*