Organic Extraction
In this conventional, widely used method, cells are lysed and cell debris is usually removed by centrifugation. Then proteins are denatured using a protease and precipitated using organic solvents such as phenol, or 1:1 mixture of phenol and chloroform, and the protein precipitate is removed by centrifugation. Purified DNA is usually recovered by precipitation using ethanol or isopropanol. In presence of monovalent cations such as Na+, and at a temperature -20°C, absolute ethanol efficiently precipitates polymeric nucleic acids and leaves behind short chain and monomeric nucleic acid components including the ribonucleotides from RNase treatment in solution. This method uses hazardous organic solvents, is relatively time-consuming, and residual phenol or chloroform may affect downstream applications such as PCR. Easy-DNA® Kit (Invitrogen) is an example