[1] Aqueous samples, lysed cells, or homogenised tissue are mixed with equal volumes of a phenol:chloroform mixture.
Care must be taken to avoid pipetting any of the organic phase or material at the interface.
This procedure is often performed multiple times to increase the purity of the DNA.
[2] This procedure yields large double stranded DNA that can be used in PCR or RFLP.
Also, because it is a two-step process involving transfer of reagents between tubes, it is at a greater risk of contamination.