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The DNA testing process can be broken down into the following five steps:
1. Sample Collection
DNA testing starts with sample collection. In most cases samples are collected by using a buccal (cheek) swab, a cotton-like Q-tip rubbed against the inside of a patient’s cheek to gather loose cells. When samples reach our lab, we divide the samples so that we can perform the test twice independently, ensuring accuracy of results.
2. DNA Extraction
We use special chemical agents to extract and purify DNA from the buccal swabs. This procedure also separates DNA from other materials found in the cells.
3. PCR
We use the Polymerase Chain Reaction (PCR) to create a DNA profile from each person’s sample. Each sample is placed in a thermal cycler (PCR machine) along with 16 fluorescent primers. These primers detect specific "loci" or locations on the DNA. During PCR, the thermal cycler takes the DNA sample mix through 30 cycles of heating and cooling. This molecular xeroxing process makes about one billion copies of each DNA loci.
4. Capillary Electrophoresis
The replicated DNA from PCR undergoes capillary electrophoresis. This process creates a map of the DNA loci produced from each sample. This map is called a DNA profile.
5. Statistical Analysis
DNA profiles from the tested parties are then compared by a trained, experienced M.D. or Ph.D. lab director to determine if there is a biological relationship among them. In an inclusion case (the alleged father is the biological father), half the child’s DNA profile will match the mother’s and half will match the father’s. If 3 or more of the child’s loci do not match the alleged father’s, he is excluded (he is not the father).
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