Electrophoresis is a common lab technique used for separating DNA fragments. DNA samples are placed in a special gel
and subjected to an electric field.
Because DNA is negatively-charged, it moves toward the positive electrode. The DNA fragments that are shortest will travel farthest, while the longest fragments will remain closest to the origin. Using the same basic principles, electrophoresis can also be used to separate RNA and proteins.
First, follow our step-by-step instructions to build a gel electrophoresis chamber using inexpensive materials from local hardware and electronics stores.
Then follow the below procedure to simulate DNA electrophoresis using food colors from your kitchen pantry.
Materials you will need:
Electrophoresis chamber, gel form and comb
Power supply that produces 50-150 volts
Agar Agar granules
Commercial food colors
Filter paper circles (cut out with hole punch)
Add 1 gram agar to 100 milliliters of water in a glass container. We show a lab flask here, but you could use a small canning jar.
Cover the container with plastic wrap. Pierce a small hole in the plastic for ventilation.
Heat the solution in the microwave oven on high power until it comes to a boil. Watch the solution closely; agar foams up and boils over easily.
Remove the container (protect your hand with a pot holder or folded paper towel) and gently swirl it to re-suspend any settled agar.
Continue this process until the agar dissolves completely.
Cool the agar until you can comfortably touch the flask.
Place tape across the ends of the gel form and place the comb in the form.
Pour cooled agar into the form. The agar should come at least half way up the comb teeth.
Immediately rinse and fill the agar flask with hot water to dissolve any remaining agar.
When the agar has solidified, carefully remove the comb.
Remove the tape from the ends of the gel form.
Make a written record of which sample you will load in each well of the gel. You may find it helpful to load samples in every other well.
Place the gel form on a black or dark surface to help you see the wells in the agar.
Fold filter paper circle in half and hold sideways using tweezers. Dip filter paper into full-strength food color to saturate.
Gently ease the filter paper into the well. Be careful not to puncture the bottoms of the wells as you load each sample. Repeat for remaining colors.
Place the gel in the electrophoresis chamber.
Make sure that the wells are closest to the negative (black) electrode.
To prepare the buffer, add a pinch of salt to one liter of tap water, deionized water, or distilled water (the water source that works for you may depend on your local water quality) and swirl to dissolve.
Fill each half of the chamber, adding solution until it is close to the top of the gel. Gently flood the gel from the end opposite the wells to minimize sample diffusion.
Place the lid on the chamber and connect the electrode leads to the power supply.
Connect the black lead to the negative terminal and the red lead to the positive terminal.
Turn on the power supply and adjust the voltage to 50-100 volts.
Run the gel for 5-10 minutes.
Once the dyes have moved through the gel, turn off the power supply, disconnect the electrode leads, and remove the chamber lid.
Remove the gel from the electrophoresis chamber and analyze your results. Did some colors move further than others? Did some colors separate into two?