The genetic material needed for the paternity test is called DNA (Deoxyribonucleic Acid) and it is found in the ‘brain’ (or nucleus) of the cells in the sample. Using the DNA sample you send in (which will be in the form of a saliva sample or blood sample) laboratories need to extract the DNA from the cell nucleus.
There are other DNA testing samples which can be used for a DNA test; these are often called non-standard sample or discreet samples (the latter terms used because these types of samples are employed when one of the people required to take part in the test is not available to provide DNA samples. A number of alternative DNA test samples can be analysed- including sperm, licked envelopes, cigarette ends and toothbrushes. Essentially, depending on the type of sample used, the chance of success in terms of DNA extraction changes.
However, before the DNA can be analysed it must first be extracted and purified from the other components (known as organelles) in the sample, a process that takes about 2-3 hours. For saliva and blood spot samples (see Collecting Samples section for information on different sample types), the laboratory analyst punches out a small circle from the filter paper on which the donor’s sample was deposited during the sample collection process. The circle of paper is transferred to a sterile tube labelled with the donor’s identification code. In the case of whole blood samples, an adequate volume of the whole blood is transferred to the labelled sterile tube.
The first step of the DNA extraction process is to break up (or lyse) the cells so that the DNA inside is released. This is achieved by adding a special solution to degrade certain components of the cell, leaving the DNA floating freely. The tubes are now inserted into a special centrifuge machine and spun at a high speed for several minutes. This causes the DNA to collect in the bottom of the tube in the form of a firm pellet, whereas the other cellular components float freely in the solution. This solution is then removed, and the remaining DNA is purified further by washing out the tube several times with an alcoholic solution which is ethanol based. Finally, the DNA is dissolved in a liquid and is ready for the next step of the paternity test.
Following these steps will ensure optimal DNA extraction. Moreover, laboratory conditions must also be monitored in terms of sterility and temperature. DNA is very stable although exposure to certain chemicals and extreme temperatures may break it down. If you think you may not be able to send in your DNA samples for a while, DNA collected by means of mouth swabs will remain unchanged for a long time, in fact for several months (around 4). For other samples that you have had for an uncertain period of time, it would be better to seek advice of the testing company to determine whether the samples are still suitable for testing.
Proceed here to read about the next steps in the process – DNA Amplification and Analysis
