With an increasing number of people joining us, we get more questions about the science behind our work than ever before. One of the most frequently asked questions we get is: "What if my cat passed away, but I still want to do a DNA test?" Here is what you need to know if you want to do a DNA test for a deceased cat.
You need to be able to collect a viable sample
In order to analyze DNA of any organism, living or deceased, one must acquire a viable DNA sample. The is the crucial first step in obtaining a DNA test. But, what is a viable sample, actually? A viable DNA sample is a sample that contains enough DNA that is not fragmented or contaminated.
Most commonly, DNA samples from living cats are collected from buccal/cheek swabs, hair follicles and/or blood. Basepaws employs the buccal swabbing method for DNA collection as buccal swabs showed to be the most efficient and accurate samples for DNA processing in the lab. DNA collection from deceased animals, however, can be a lot more challenging. Most commonly, DNA from deceased animals is obtained from fur and/or tissue samples.
Important remarks about fur samples
Basepaws' DNA extraction and analysis methods are well-optimized for fur samples, but hair sampling can still be challenging. It is often assumed that shedded hair collected from cat toys, brushes and furniture is an ideal source for DNA extraction. However, this is usually not the case. DNA can only be obtained from the hair follicles, not actual strands of hair. This is because DNA can be collected only from cells whose life cycle is not over and whose nucleus is not already degraded (which is the case for any hair that falls out/sheds naturally on its own).
DNA is obtained from epithelial cells around the hair follicle. This means that if the hair fell out on its own, it is quite unlikely that there will be any DNA left suitable for analysis. Hairs pulled out directly from the animal will make for a much more reliable source of DNA. This is because when hair is taken directly from the root, the epithelial cells from the follicle are still attached. This is crucial, which is why Basepaws asks its customers to obtain hair directly from their cats, and a fairly large amount of it too.
How to sample DNA from a deceased cat?
So...is it even possible to collect a suitable fur sample from a deceased cat? In theory, yes. In practice, there are certain challenges to overcome. The fur samples can be hard to obtain from deceased cats and there are several things you need to keep in mind:
1. The fur needs to be collected directly from the animal. While a hair sample does not necessarily need to be collected from a living animal, as explained above, a sample has to be collected directly from the actual animal. Unfortunately, hair collected from toys, bedding, grooming tools or cut off the body most likely will not contain viable epithelial cells needed for DNA extraction.
2. The sample can only be obtained if the death was recent or the animal has been preserved below freezing conditions. DNA can often be collected successfully if the death was recent. If the time of death is not recent, DNA can still be extracted as long as the animal has been preserved below freezing conditions. It is important to remember, however, that the animal should not have been preserved for longer than two weeks. This is because once the cells die, DNA begins to rapidly deteriorate.
3. Do not defrost the preserved cat prior to sampling. In case you have had your cat's carcass in a freezer, and it's been less than 20 days or so after death, you can try to collect a fur sample but it is not advised to allow the cat to "defrost" first. Additionally, since plucking hair off a frozen body without snapping off the strand can be challenging, it is advisable to provide us with a tissue sample along with the hair (by cutting the follicle & its hair out of the skin). This sample will need to be placed on ice immediately. Any "thawing" of the tissue/hair can pretty much kill any DNA that may still be there.
4. Old samples are usually not viable. If a cat has been dead for longer than 20 days, if it has been stored at room or warmer temperature or if the sample itself is old, the chances of getting any DNA are slim to none.
Do you have more questions about DNA tests for a deceased cat we didn't cover with this blog? Please drop us a message on social media or an email to email@example.com.
To learn more about DNA and the science behind our DNA analysis please read our blog about Behind the scenes at Basepaws. Here you will find information about DNA sampling, extraction, sequencing and the Basepaws database.