The PM plus DQA1TM (PE Applied Biosystems) typing kit targets six genetic loci. All six are copied in the initial PCR. The products from this reaction are then placed onto two separate typing strips. One strip is for DQ alpha and the other types the remaining five loci.
There are several steps in a DQ alpha PCR test:
1. DNA from 50 or more cells is extracted. Notice that this test requires fewer cells that the RFLP test. Sensitivity (the number of cells needed) is the main advantage of PCR tests. However, the increased sensitivity also makes PCR tests more vulnerable to trace contaminants, DNA from unexpected sources, in other words.
2. The DNA from the sample is copied over and over resulting in amplification of the original target sequence. The copying or amplification is accomplished in a machine specially designed for this purpose. This machine is called a thermal cycler.3. The amplified DNA is now treated with a variety of probes that are bound to a blot (see RFLP: Note: In RFLP, the target DNA is bound to the blot and the probe DNA is added. For the DQ alpha dot blot, the probe DNAs are bound to a small blot strip and the target DNA is added).