Create the gel matrix by following the directions on the container of gel media. Most gels are made between 0.7% and 2% agarose. The lower end agar concentration will give good separation of DNA fragments between 5 and 10kb, while a 2% gel will show good separation for smaller fragments (0.2--1kb). When the agarose is cooled to just above hardening, add ethidium bromide to the gel at a concentration of 10mg/mL. Swirl to mix before pouring, being careful not to create bubbles. Be sure to insert the combs while the gel is soft so that wells are created for the DNA samples. Let gel harden for at least 30 minutes before loading samples.
Make buffer solution. A standard buffer for gel electrophoresis is Tris-Borate-EDTA, which can be made by dissolving 218g Tris base, 110g Boric acid and 9.3g EDTA in 1.9L of distilled water. Use NaOH to carefully adjust the pH to 8.3. This gives a 10X solution. Dilute to make a batch of 0.5x solution to use in the electrophoresis machine.
Place gel in the electrophoresis machine, and cover with a buffer solution.
Mix 2--4µL of each DNA sample with about 5 µL of dye.
Load first well with marker and dye.
Begining with the second well, begin loading each sample. Finish with the final lane loaded with the same marker.
Close the gel machine and turn on the power. Run the gel at 5V/cm.
Turn off power source when loading dye has reached near the other side of the gel. Be careful to monitor the gel so that the loading dye doesn't run off the other end of the gel.
Remove gel from tank and view in a dark room under a UV light.
Note the marker on the ladder that is the size the wild-type (non-mutant) DNA fragment is expected to be. If the sample is pure, the corresponding band of the samples is the wild-type and all other bands represent mutants.