DNA sampling and storage

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By Lies Klösters, february 2009

Why should we store DNA?

More and more research is being done to determine the loci of certain diseases. And thus it becomes more and more important to perform DNA tests on our pets. But what do you do when you want to test a pet that already passed away? Or one that has been rehomed, and where the new owners are not cooperative to give you DNA from their pet? The answer is: take DNA samples from your animals while they are still living in your home.

You can take not only DNA from the adults, but also from the offspring you've bred, before they leave your house. That way you can always test all those animals later on.

The disadvantage is that the identity of the animal can not be verified if you test DNA from such a sample. But you can do this for your own knowledge, so you could trace the origin of a certain disease and you can adapt your breeding program accordingly.

How long can DNA be stored?

When you take a DNA sample in the prescribed way, it can be stored for many years. The proper way to store DNA is to take a sample that has not been contaminated by DNA material other than that of the animal you want to take a sample of. The sample is best kept at room temperature, in a dry place. (See below for further instructions.) And if you need to ship it to a laboratory for DNA analysis, you can send it by regular mail.

Warning: A DNA sample can be rendered useless when it starts to mold, or when it is treated with material that can affect DNA, like e.g. disinfectants.

Do I need a blood sample to perform a DNA test on my animals?

You don't always need blood to perform a DNA test. DNA is extracted from the nucleus of cells. These cells can be from different types of tissue, such as blood, cheek cells, semen or the roots of hair.

Taking blood samples from your animal can be stressful because you have to take it to the vet and blood has to be drawn from your pet. Cats often have more problems with going to the vet than dogs, although there are also cats who are not impressed by the vet at all.
In the case of a hair sample, you have to pull out your pet's hair and make sure the roots also come out. This can be a difficult technique if you have an animal with very fluffy hair which flies away easily. For horses, pulling hair is a technique that is often used for DNA testing; the hair from the tail or manes are very much suited for this type of DNA collecting.
Collecting semen from an animal is not always easy, depending on the animal species you work with. For cats e.g., it is not a used as a source for a DNA sample because it is difficult to collect semen from cats. For dogs or several other species semen can be used as a DNA ample. Obviously you would still need another technique to collect DNA from your females.

The buccal swab is a low invasive way of collecting DNA and cheek cells are just the same for a DNA analysis as any other type of cells. So unless there is a specific need for a blood sample, you can use a mouth swab.

How to collect DNA samples by using mouth swabs:

  1. It is the best to order sterile cotton tip applicators either on the Internet or from your pharmacy store. But if this is not possible, you can also use ordinary cotton tips. Make sure you don't touch the cotton tip with your hands. If bacteria from you hands transfer onto the swab, the bacteria can ruin your DNA sample.
  2. Start with one animal, and finish this procedure entirely before you start with the next one.
  3. Wait at least 15 minutes -if your pet has recently eaten- before you collect the sample. Right after an animal has eaten, there can still be traces of food in the mouth which can be a source of energy for bacteria.
    And, if you are taking samples from nurslings, you could contaminate it's DNA with the mother's DNA if there are still traces of milk in the mouth. But also adults who have been eating recently, can have foreign DNA in their mouth. So it is important for several reasons to wait long enough after a meal before taking the DNA sample.
  4. Open de end of the packaging sleeve at the opposite side of the cotton tip. Do not touch the cotton tip with your fingers! You will contaminate the sample if you bring bacteria (or your own DNA) on the cotton tip.
  5. Hold the cotton tip, half-way down the handle, in the hand that you use for writing.
  6. Hold your pet by the scruff with the other hand and place the cotton tip between the cheek and gums. Twirl the cotton tip several times to get the sample.
  7. Let the cotton tip air dry for 30 seconds. Do not blow on it! By blowing on the cotton tip you can blow minuscule parts of your own saliva on the cotton tip, and again, you could contaminate the sample.
  8. Place the cotton tip back in the packaging sleeve and seal the sleeve with tape or a staple. The seal should not be air tight! A wet cotton tip in an airtight sleeve may grow bacteria and destroy the sample.
  9. Take at least 5 samples per pet. Collect all the cotton tips used for one pet together in one envelope, labeled with your pet's full name and the date when you took the sample.
    If you are sampling a very young animal that might not have a name yet, at least note the name of the parents and other characteristics (colour, sex, or other specifics that can help you later on to remember whose DNA it is) on the label or envelope. Years after you have taken the sample, it might be confusing whose DNA is in the envelope if the information on the package is not sufficient.
  10. The swabs can be stored at room temperature.