Molecular cloning experiments rely greatly on the isolation and analysis of defined DNA fragments. Agarose gel electrophoresis and polyacrylamide gel electrophoresis (reviewed in 1-11) are simple, yet powerful, high-resolution methods of separating specific DNA fragments on the basis of size and conformation. Recovery of pristine DNA, from these gels, is a prerequisite for the study of genome structure and function. Agarose gels resolve DNA from 150 to 880,000 base pairs at agarose concentrations from 0.1 to 2.5%, while acrylamide gels ranging from 3 to 20% provide good resolution of fragments ranging from 10 to 2000 base pairs (10). Ever since the first set of methods aimed at extracting DNA from agarose were published (2-4, 12-14) a plethora of techniques have been devised. The availability of a myriad of methods, to extract DNA from gel slices, could be construed to mean that a single method has not been universally accepted as the norm for recovering DNA from gels. This is particularly evident in the case of recovering DNA from agarose gels.
Generally, the size range of the sample will serve to determine the choice of gel for both analytical and preparative work. As a generalization, agarose is uti-