How do the scientists performing your DNA paternity test see the DNA? DNA molecules are very small, so small that actually seeing the DNA is very difficult and requires special techniques and equipment.

The insides of your cheeks will be swabbed to provide DNA for your paternity test. This pulls thousands of cells off of your cheeks onto the swab. Each cell contains two sets of DNA molecules. One set comes from your father and another from your mother. After your DNA samples arrive at the paternity testing laboratory they are processed using a special set of chemicals to extract and purify the DNA from each individual cell. It is this purified DNA that is used to perform you DNA paternity test.

Most DNA paternity tests are performed using a technique called PCR which stands for Polymerase Chain Reaction. PCR is a way of taking a small segment of DNA and making many copies of it. Additionally when the copies are being made the copies are having a fluorescent markers attached to them.

The portions of the DNA that are examined for your DNA paternity test are called STRs which stands for Short Tandem Repeats. When PCR has run its course there will be millions of copies of STRs where there were originally only a few copies, all of them tagged with fluorescent markers.

Each set of STRs is its own length, some are longer than others. So the next step is to determine the various lengths of these STRs. This is done using Electrophoresis. Very basically electrophoresis pulls the DNA through a gel that separates the fragments by size. The larger fragments of DNA move through the gel more slowly, the smaller fragments more quickly. Here is where those fluorescent markers come into play. A laser passes through the gel, whenever the laser hits a fluorescent marker, that marker puts out a fluorescent glow. Where on the gel that the DNA fluoresces, tells the scientist performing your DNA paternity test how long that fragment is.

One set of the child's STRs will have originated from the mother and another set of STRs will have come from the father. These sizes are determined for all the individuals involved in the test and compared to give you the results of your DNA paternity test. The DNA analyst then looks for matches in fragment size between the child, mother, and alleged father. The sizes that the child and mother share help to determine the fragments that the child received from the father. If there is a match a statistical calculation is performed. If there is no match the alleged father may be excluded.