||DNA is prone to damage under the attack of free radicals (such as ·OH), that is, deoxypentose is broken, the diphosphate bond is broken, and the base is broken or shed, which can further produce single-strand break or double-strand fracture. Fix the cells in low-melting agarose, apply a small amount of cells on a glass slide, destroy the cell membrane with an alkaline high-salt solution, and untwist the DNA molecules with the alkaline solution. Place the slide in the electrophoresis solution, and under the action of the electric field, the DNA molecules move towards the anode. If the DNA damage is severe and there are many fragments, the electrophoresis speed is fast. Undamaged DNA macromolecules stay in place due to the barrier of the cell membrane. With EB, PI staining or silver staining, it can be observed that cells with damaged DNA resemble comets, for qualitative analysis. Related software can also be used for quantitative analysis.