DNA extraction with organic solvents:

Extraction with organic solvents is a convention method where the cell lysate treated with detergents are mixed with a definite proportion of phenol, chloroform and isoamyl alcohol. Here the protein and other contaminants are separated with organic phase and the DNA remains in aqueous phase, which can be further precipitated with alcohol. The procedure is comparatively time consuming and use of several toxic chemicals may interfere with downstream applications. Phenol is the most common interfering agent. This method is used for general DNA applications and not suitable for sensitive and high throughput applications.

DNA extraction with Cesium chloride (CsCl) density gradients:

CsCl density gradient method yields good quality of DNA, suitable for several downstream applications but, the use of toxic chemicals, comparatively longer time consumption and extensive labor restrict the usefulness of this method. The crude cell lysate was precipitated with alcohol. Resuspende the DNA and mixed with CsCl + EtBr. Centrifuge the mixture in a ultra centrifuge at high speed for longer time to collect the DNA in a single layer. The DNA layer was extracted with isopropenol to remove the EtBr. The DNA was then precipitated with ethanol.

DNA extraction by anion exchange chromatography:

Anion exchange chromatography method is comparatively faster and yields high quality of DNA which can be used for several purpose. This method doesn't required any toxic chemicals and intense labor, which makes it popular and can be adopted for routine purpose.

As clearly reflected with the name this method involves the exchange of anions. The matrix is positively charged and interacts with negatively charged phosphate group of DNA in low salt condition. The cell lysate was passed through matrix, which binds the DNA. Protein and other contaminants were washed with medium salt buffer and DNA was eluted with high salt concentration. The Eluted DNA was then precipitated with alcohol.