What is the role of phenol in DNA extraction from whole blood?

Question

What is the role of phenol in DNA extraction from whole blood?

Answer 1

Extraction with phenol and phenol/chloroform mixtures is a universal method for purification of DNA and RNA. Proteins and restriction enzymes are removed by phenol and chloroform in disrupting protein secondary structure causing proteins to denature and precipitate from solution. Although each of these solvents is capable of performing this function alone, the two materials together remove proteins from solution much more effectively. Nucleic acids are recovered in the liquid phase.

During phenol extraction, the precipitated proteins collect at an interphase between the aqueous and organic layers. It is very important to understand the effect of pH on the performance of phenol.

For the purification of DNA, the use of phenol at pH above 7.0 is desirable in order to collect DNA in the upper aqueous layer of a phenol extraction (phenol saturated, pH8). At lower pH (4.5), DNA and proteins are collected at the interphase although RNA can be collected in the aqueous phase (phenol saturated, pH4,5