STEP 2: Alkaline Lysis: Bacterial cells are treated with lysis solution II containing 0.2 N NaOH and 1% SDS. to lyse the cells and denature DNA (both chromosomal and plasmid DNA).
STEP 3: Renaturation: In 3rd step, denatured DNA is renatured with solution III containing potassium acetate, glacial acetic acid. In this step small DNA (plasmid)
renatures
back quickly whereas chromosomal DNA remained denatured.
STEP 4: Deproteination: Resulting supernatant containing plasmid DNA and protein is treated with phenol: chloroform: isoamyl alchol mixture to remove protein in the precipitate where as plasmid remained in solution.
STEP 5: Precipitation : plasmid is precipitated by 100%
alcohol
from the solution.