Buffer and reagent for electrophoresis- The purpose of each reagents used in horizontal gel electrophoresis are  as follows-

1. Agarose-polymeric sugar used to prepare horizontal gel for DNA analysis.

2. Ethidium bromide- for staining of the agarose gel to visualize the DNA.

3. Sucrose-For preparation of loading dye for horizontal gel.

4. Tris-HCl- The component of the running buffer.

5. Bromophenol blue-Tracking dye to monitor the progress of the electrophoresis.

Casting of the agarose gel- Different steps to cast the agarose gel for horizontal gel electrophoresis are given in Figure 36.2. The agarose powder is dissolved in a buffer (TAE or TBE) and heated to melt the agarose. Hot agarose is poured into the gel cassette and allowed it to set. A comb can be inserted into the hot agarose to cast the well for loading the sample. In few cases, we can add ethidium bromide within  the gel so that it stains the DNA while electrophoresis.

Figure 36.2: Different steps in casting of the agarose gel for horizontal gel electrophoresis apparatus.