Practice question

Phenol-chloroform extraction separates nucleic acids based on differential solubility. Phenol denatures proteins and chloroform improves phase separation and removes lipids. When mixed with aqueous lysate and centrifuged, two phases form: lower organic phase containing phenol-chloroform and hydrophobic molecules, and upper aqueous phase containing hydrophilic nucleic acids. DNA, being highly polar due to its phosphate backbone, remains soluble in the aqueous phase, while denatured proteins partition into organic phase or precipitate at interphase. Thus pure DNA is recovered from the aqueous layer for subsequent precipitation.