(1) sample preparation: firstly, DNA or RNA needs to be extracted from the tissue sample to be detected. DNA should be digested with restriction endonuclease to produce fragments with specific length, and then the digested products should be separated by gel electrophoresis according to molecular size. Generally speaking, DNA molecules have their own unique restriction endonuclease maps, so after digestion and electrophoretic separation, specific bands can be formed on the gel. After denaturing the gel containing DNA fragments, it was directly transferred to the supporting membrane and firmly combined with it. In this way, the position of these detection fragments on the gel is directly reflected in the transfer on the membrane. RNA samples can be directly separated by electrophoresis under denaturing conditions, and then transferred, crosslinked and fixed.

(2) Preparation of probe: A probe refers to a nucleic acid fragment that can combine with the nucleic acid molecule to be detected according to the principle of base pairing. It can be a piece of DNA, RNA or synthetic oligonucleotide. In nucleic acid hybridization experiments, probes need to be labeled with directly detectable elements or molecules. In this way, by isolating the probe molecules of nucleic acid molecules bound to the Yin En membrane, we can not only know the position of the detected nucleic acid fragment on the membrane, that is, on the electrophoresis gel, but also know its molecular size.

(3) Hybridization: First, pre-hybridization is needed, that is, nonspecific binding sites on the membrane are blocked with nonspecific nucleic acid solution. Because the nucleic acid molecules transferred to the membrane are already denatured molecules, it is only necessary to denature the labeled probe during hybridization, then let the probe react with the membrane at a specific temperature, and then wash away the unbound probe molecules.

(4) Detection: According to different methods of labeling probes, the detection methods are also different. Radioisotope labeled probes need autoradiography to detect their position on the membrane; However, if the probe is labeled by non-isotopic methods such as biotin, it needs to be detected by corresponding immunohistochemical methods.