Why tris saturated phenol is used in DNA extraction?
The phenol acts as an organic solvent, and serves to remove proteins and other organic junk from the cellular soup. In addition, since the phenol is denser than the aqueous layer, the heavy debris (bone and tissue fragments, hair, etc.) will be centrifuged down to the bottom of the tube, below the phenol layer and therefore also out of the DNA-containing aqueous layer. The Tris-buffer saturation is done to reduce or eliminate the problem of the aqueous DNA soup being taken up by the phenol. If the phenol mix is already saturated by an aqueous material (the Tris buffer), it will not be able to absorb any of your DNA solution. Tris is used to buffer the aqueous soilution from being affected by the acidic phenol mix (phenol = carbolic acid, a “weak”, but very caustic acid). Phenol extraction is very effective, but also rather undesirable, as phenol is both highly caustic and somewhat toxic in poorly-ventilated areas (especially when mixed with chloroform, as is generally the case for extr
