Gel extraction
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In molecular biology, gel extraction or gel isolation is a technique where viable DNA is extracted from an agarose gel following agarose gel electrophoresis in order to isolate a specific band. To perform this feat, UV light is shone on the gel to illuminate all the ethidium bromide-stained DNA. The desired band is identified and physically removed (i.e. with a cover slip or razor blade). The removed gel should contain the desired DNA inside. It is placed in a dialysis tube that prevents DNA from passing through and soaked in TE buffer. The gel-contained tube is run through gel electrophresis long enough so that the DNA is removed from the gel but remains in the tube. The tube solution can then be pippetted out and will contain the desired DNA with minimal background.
The disadvantage of gel isolation is that background can only be removed if it can be physically identified using the UV light. If two bands are very close together, it would be hard to separate them without some contamination. The advantage is ease-of-use.
