DNA testing can be carried out with many different samples. Even the smallest traces of genetic material can provide enough DNA to extract a genetic profile of the person to which the sample belonged.
Which sample do I choose?
In the vast majority of cases, the choice of samples you can actually use will be limited to one or perhaps two. Often people think that DNA can be extracted from any source but the truth is that often this is unlikely or if possible, would be far too costly for a normal direct-to-consumer DNA test. Forensic films often show experts successfully extracting DNA from the lip mark of a glass or from a single cigarette end and whilst this is possible, it requires much more thorough and advanced forensic DNA testing laboratory.
So which sample do you chose? If everyone involved in the test is actually aware of the test and willing to be tested the answer is simple: all test participants can collect their own samples of genetic material by using oral swabs. All one needs to do is rub the swab inside the mouth, under the tongue and inner cheek for about ten seconds and then allow it to dry. This sample is ideal because it always offer a high probability of successful DNA extraction.
If collecting samples with orals swabs is not possible you will need to discuss other samples which might be viable for a DNA test; perhaps nail clippings, used Kleenexes or plucked hairs. The probability of successful DNA extraction will vary depending on the type of sample you use. A used Kleenex offers a 95% success rate whilst a cigarette end offers a 65% success rate. Whilst DNA can also be extracted from a licked envelope the chances of a successful extraction of a DNA profile is of only 25% with this sample.
How do I collect and store the sample?
Different samples might require a different method of sample collection and storage. Oral swabs are the easiest because they can just be placed in a paper envelope and sent for testing. The vast majority of DNA samples should be placed in a paper envelope. Nails clippings or hairs are ideally collected with a pair of tweezers. The most problematic sample to collect, store and post is blood. Medical blood draws are a bit of a hassle to collect; postage of such as sample is also problematic- not only does it need to be packaged in such a way that the sample collection tube does not leak or break, but the sample itself will need special labels and an official certificate declaring that it is free of pathogens.
Postage and storage is not such an issue with other samples – you can in fact test a DNA sample that is several weeks old so as long as it has not been exposed to extreme temperature or chemical solutions that may have altered the DNA.