activity page will offer:
Assemble a gel chamber for separating mixtures
separation influenced by electric charge
define separation through gel electrophoresis
- Plastic ice cube molds
- Aluminum foil
- 9 volt battery
- Connecting wires with alligator clips
- Buffer solution (as prepared by your instructor)**
- Medicine dropper (or fine laboratory pipette)
- Warm liquid agar solution ***
- Food coloring (various colors)
Prior to this activity, use a small saw to carefully separate
a plastic ice cube tray into sections with 2 or 4 individual
Prepare 1 gram of baking soda in 100 ml of water
*** Prepare 1.0 grams non-nutrient agar in 100 ml of water.
Agar is available at health food stores.
1- Setting the Gel
- Clean and dry two mold chambers of an ice cube tray.
- Obtain the cooling agar solution as prepared by your instructor.
- Carefully pour this solution into each of the tray chambers.
- Leave undisturbed or place the tray in a refrigerator
to accelerate solidification of the gelatin.
2- Building the Chamber
- Construct a blade-like tool to cut into the solid gel
by folding a piece of aluminum foil into a stiff rectangle
about 1 cm wide by 5 cm long. The "blade" should have the
thickness of about five sheets of foil.
- Use this folded strip to poke a slot-shaped well into
the gelatin. The well should be positioned at about the
midline of the chamber. Use this tool to poke, cut, and
remove the gel material so that a thin (less than 1 mm)
rectangular slot is created.
- Cut two strips of aluminum foil (about 1 cm by 4 cm) for
the chamber electrodes. Insert these along opposite inner
sides of the mold.
3- Running the Sample
- Flood the agar surface with buffer solution. A layer of
about 3 mm of buffer must cover the top of the gel and fill
the rectangular well.
- Fill your pipette or medicine dropper with green food
coloring. Immerse the tip in the buffer and position it
at the bottom of the well. Slowly release some of your sample
and observe how if flows upward and fills the well. Continue
releasing the sample until the well is filled. Carefully
remove the tip of the pipette or dropper from the chamber,
trying not to disturb the buffer solution.
- Use alligator clips to connect a 9-volt battery to the
exposed tops of the aluminum foil terminals. Wait one hour.
- Examine the gel. What do you see?
NOTE: You can increase the speed of the separation by wiring
up several 9-volt batteries in a series.
- Reattach the electrodes and continue examining the gel
at 30-minute intervals. Record your observations.
- Repeat this procedure on other food coloring samples using
the remaining gel chambers.
- How has the gel changed?
- Did the coloring spread out evenly in all directions?
- Did the green food coloring change shades? Which Traveled
- Did the other food colorings separate into the same bands
as the green?
instructor can demonstrate a much quicker separation using
a laboratory power supply that produces about 45 volts. At
this voltage, a satisfactory separation of food coloring is
achieved in about 30 minutes time.
of DNA have an overall negative charge. If you were to perform
electrophoresis on DNA, at which side of the well would you
observe the formation of DNA bands? Why?
examining the separation bands of DNA, you discover that the
smaller fragments of DNA travel the greatest distance from
the well. Why?
you know that this same technique is used to create a confirmatory
test of HIV called the Western blot assay? HIV proteins are
obtained from laboratory cultures and separated out using
gel electrophoresis. These distinct and characteristic bands
are "blotted" onto a test strip. The test strip is placed
in contact with blood serum samples. If the serum contains
HIV antibodies, it will bind to the specific protein bands
and confirm a previous exposure (and immune response) to HIV.
Conduct a search on the World Wide Web to learn more about
- An Interactive Study Guide
A great introduction and overview of DNA, mapping, and gel
This site as step-by-step instructions for constructing a
sturdy classroom electrophoresis chamber using Plexiglas.
Gel Electrophoresis of DNA
An advanced site for instructors showing how to prepare and
run DNA gels.
more Web links on this topic - visit our Resources
activities in this guide were contributed by Michael DiSpezio,
a Massachusetts-based science writer and author of "Critical
Thinking Puzzles" and "Awesome Experiments in Light & Sound"
(Sterling Publishing Co., NY).
Academic Advisors for this Guide:
Corrine Lowen, Science Department, Wayland Public Schools,
Suzanne Panico, Science Department, Fenway High School, Boston,
Anne E. Jones, Science Department, Wayland Middle School,