DNA Extraction is the removal of DNA from the cells in which it normally resides. Chelex is a polyvalent chelating agent that is presumed to prevent the degradation of DNA by chelating metal ions that act as catalysts in the breakdown of DNA. The Chelex technique developed in 1991 can be used as a preparation for PCR only. The Chelex technique generally recovers single stranded DNA using a procedure that adds a “chelating-resin” suspension directly to the specimen (blood, bloodstain, semen for example) followed by an ion-exchange resin that binds the polyvalent metal ion, magnesium. In the last step, the metal is taken away bringing other material with it. The first step in the DNA extraction procedure is to boil a small amount of tissue in a Chelex solution. The boiling helps to break up the cells in the preparation, and denatures proteins. The Chelex protects the sample from DNAases that might remain after the boiling and could subsequently contaminate the samples. A chelex-base method is recommended for DNA preparation as this does not require any tube-tube transfers, is quick and produces a standard quality of DNA that is reliable in PCR multiplex assays. The method has proven to generate reliable results with small samples and therefore it is recommended that all samples be tested regardless of sample size/volume.
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