DNA Testing
Steps to DNA Testing
DNA testing can be performed for a variety of reasons ranging from paternity testing to determining who was involved in a criminal activity. It is also widely used in the field of agronomy and agriculture to study different varieties of a number of different plants. No matter what the case DNA might be used it is one of the most important tools that scientists have in their belt nowadays to help them better understand how everything in nature works. For the criminologist it is the silent evidence – it tells the story of who was where even when there are no witnesses around.
Many of us know about DNA from such shows as “CSI” and “Law and Order”. Though often “enhanced” for ratings effects, the principle behind the techniques that these shows use is the same as it is in most laboratories – find the DNA sample, extract it, determine its usability and match it against a known sample. The practice of DNA testing has roots back to the 1980's when the FBI in the United States began to use it for helping identify suspects. Today, DNA testing has become so routine and part of our society that it can be performed through in-home testing kits that are readily available for less than $100 on the open market.
So how does DNA testing work and what are the steps behind it? To begin with, DNA testing is quite simple actually – and it is because of this simplicity that the practice of using it has skyrocketed. The basic procedure involves the collection of a sample, the separation of bands via the use of probes and the matching of those bands against known DNA samples. The most complex step is the separation of bands, but even that has been mostly automated to the point where a well-trained laboratory technician can perform the procedure in less than 30 minutes. In fact, many organizations that do DNA testing are now turning to completely automated equipment that can extract the unknown DNA sample, create bands and run comparisons against known DNA. All of this happens without the intervention of a human in the entire process except for the initial collection procedure.
The most common way to collect DNA samples is through the use of a buccal swab. Resembling the cotton swabs in many bathrooms around the world, the buccal swab is rubbed gently against the inside of a subject's cheeks to collect cells. The swab is then placed in a test-tube like container for shipping and to prevent contamination. The unique thing about these swabs is that they require no refrigeration and the sample can last for years in storage. This is a major step forward from the days when blood samples had to be used for DNA testing that required almost immediate processing in order to extra usable DNA samples.
Once the DNA is collected it is sent off to a laboratory for analysis. Through the use of a gel matrix the DNA is exposed to probes that generate unique bands. These bands can be matched against a known DNA sample. If the bands match, you have the probability of a match. The more probes that you expose the DNA sample to, the more unique bands that will be generated which can be used for more exact matching. Results can be generated in a matter of hours in most cases, and with uncontaminated specimen and known samples a match can be guaranteed up to 99.999% accuracy.