The pellet was dried, re-suspended in 200 ml of TE buffer (10 mM Tris–HCl, 0.1 mM EDTA, pH 8.0) plus 20 μg of RNase, and then incubated overnight at room temperature.The DNA solution was mixed with 20 ml of 8 M ammonium acetate and 400 ml of cold absolute ethanol for 30 min, centrifuged for 10 min, and air dried at room temperature.