Comparison of different methods of recovering DNA from a methylation assay

Several enzymes, for example DNA (cytosine-5-)-methyltransferase, produce relatively strong interactions with DNA and hinder the quantitative recovery of this DNA from a reaction mixture. Classical methods like the Sevag chloroform-iso-amylic alcohol one or the phenol procedure lead only to a 50-60 per cent recovery of the DNA. A new procedure was worked out utilizing pancreatic RNase, proteinase K, NaOH 0.5 M treatment and trichloracetic acid precipitation which gives 85 per cent recovery of DNA.