Phenol Chloroform Extraction is a method used for extracting DNA from blood stains and liquid blood. Bloodstains or liquid blood are placed in a centrifuge tube. The stain extraction buffer (salts, detergents, buffer,10mm tris,100 mm NaCl, 39Mm Dithioreitol (DTT) ,10 Mm EDTA, 2% SDS (sodium dodecyl sulfate) is added. Salts and detergents help solubilize cell components. DTT reduces and breaks apart disulfide linkages. Proteinase k is used to digest proteins. Phenol Chloroform isoamyl alcohol is added to form a milky emulsion and centrifuged to form a bilayer. The aqueous layer contains the DNA, interphase contains the protein, and proteins lipids can be seen in the organic layer. DNA can be precipitated using 100 % ethanol and then washed with 70 % ethanol solubilized in a buffer
Cigarette butts, envelope flaps, saliva stains are treated as bloodstains. In the case of hair, the hair must be rinsed in 100 % ethanol, water, and rinsed in xylene. The bottom part (cm) of the hair is removed, treated with extraction buffer, proteinase k, and should be treated as a bloodstain.
Bone powder (10 mg) should be incubated at 37c for 16 hours in 0.5ml EDTA for decalcification. Centrifuge and remove EDTA. Wash the powder with ultrapure water preferably 3 times. Extraction buffer and proteinase k were added along with the powder and incubated in a shaking water bath at 56C for 8 hours. DNA is extracted using phenol-chloroform isoamyl alcohol and should be purified using ethanol.