1. Phenol extraction method: first use eggase K and SDS to disrupt the cells, digest the protein, and then extract with phenol and phenol-chlorine. After high-speed centrifugation, take the supernatant. The size of the DNA obtained is 100-150kb.

2. Formamide depolymerization method: disrupt the cells as above, then use high-concentration formamide to depolymerize the combination of protein and DNA, and then dialyze to obtain DNA to obtain DNA of about 200kb.

3. Glass rod winding method: lyse cells with guanidine hydrochloride, spread the lysate on ethanol, then use a hook or U-shaped glass rod to gently stir the interface, and wrap the DNA precipitate around the glass rod. Generate DNA of approximately 80kb.

IV. Isopropyl alcohol precipitation method: basically the same as method 1, only using twice the volume of isopropyl alcohol instead of ethanol, small molecule RNA (soluble in isopropyl alcohol) can be removed

5. Rapid surfactant preparation method: use Triton X-100A or NP40 surfactant to disrupt cells, then use proteinase K or phenol to remove proteins, ethanol precipitation or dialysis.

6. Rapid preparation by heating method: heat at 96°C-100°C for five minutes, then centrifuge and take the supernatant, which can be used for PCR reactions.

7. Rapid preparation of alkali denaturation: first react with NaOH for 20 minutes, then neutralize with HCI, centrifuge and take the supernatant, which contains a small amount of DNA.