Tami Maus, Sue Seim, Linda Wiessner and Patrick Williams
Memorial Blood Center of Minnesota, Minneapolis, MN

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The isolation and purification of high quality DNA is essential for RFLP based paternity testing. A number of methods have been developed for the extraction of DNA from whole blood, each having its own strengths and weaknesses. These methods generally consist of two parts: a method to gently lyse the cells and solubilize the DNA, followed by one of several enzymatic or chemical steps to remove contaminating proteins, RNA, or other macromolecules. Proteinase K, followed by Phenol or high salt precipitation has been commonly used for the isolation of DNA. In the present study, we have examined the use of the QIAGEN (QIAamp) extraction method for whole blood samples and compared its performance to our standard extraction protocol. The standard extraction procedure begins with 3mls of whole blood and incorporates steps for the lysis of red cells, lysis of white cells, protein precipitation, DNA precipitation, followed by rehydration of the DNA. This procedure requires long incubations and extended centrifugation, making it time consuming and labor intensive, but yields an average of 90 µg of DNA per sample. The QIAGEN procedure begins with the harvest of 200 µl of buffy coat followed by cell lysis and the binding of the DNA to a silica resin. Contaminants are then washed from the sample and the DNA is eluted from the resin. Incubation times are short and no additional rehydration time is necessary before quantitation. A rack of 72 samples can be processed in approximately two hours, with an average yield of 41 µg per sample. Restriction analysis of the DNA samples indicated that the QIAGEN procedure results in equally high quality DNA, while saving a significant amount of time and labor.