Abstract: Obtaining specific DNA fragments is a prerequisite to carry out varieties of molecular biology experiments and polyacrylamide gel electrophoresis is the first choice to purify specific DNA owing to its high resolution. In this assay, by exploiting the curing effect of liquid nitrogen, an approach applying grinding to break the structure of polyacrylamide gel electrophoresis to extract and purify DNA is introduced. The DNA purified according to the method above and the counterpart based on the purification of agarose gel electrophoresis are subjected to further detection through polyacrylamide gel electrophoresis, with the result manifesting, the DNA purified via the method above has a higher purity and specificity as well as an equal efficiency comparing with the one purified by agarose gel electrophoresis. The method described here improves the specificity of DNA, and simultaneously being economical, efficient and less time-consuming, thus it worth using widely.

Key words: Non-denaturing polyacrylamide gel, Agarose gel, Small DNA fragment recovery and purification, Electrophoretic mobili-ty shift assay