After adding chloroform and homogenizing, the mixture was centrifuged and divided into three layers, including the upper colorless aqueous phase, the middle phase, and the lower red organic phase. The RNA was dissolved in the aqueous phase, and after removing the aqueous phase, the protein could be precipitated with isopropanol to obtain purified RNA; the soluble substances in the middle phase and the lower red organic phase could be precipitated with anhydrous ethanol to obtain purified DNA. There should be no protein contamination in theory.