NAME:______________________PERIOD:____DATE:________
Lab: Rainbow Electrophoresis
Introduction:
Gel electrophoresis is a method of separating molecules based on their charge,
size, and shape. When an electric current is applied to the gel, negatively charged DNA
molecules move toward the positive electrode. How far the molecule moves through
the gel depends on the size. The bigger fragments of DNA move shorter distance and
the longer fragments of DNA move a longer distance.
The next step is staining the DNA. It is necessary because DNA is not normally
visible in the gel. The gel is soaked in a staining solution and makes the bands visible.
These are the bands that you may have seen in examples of DNA fingerprinting. Each
band represents a piece of DNA of different size. After staining, the gel can be
photographed for a permanent record.
In this investigation, you will compare the rate and direction of movement of
several different dye samples in an agarose gel and draw conclusions about their
charge and chemical composition based on your observations.
Materials:
 Electrophoresis chamber and power source
 6 test tubes with various food colors
 6 pipettes, one for each color (be sure to not cross contaminate)
 Paper Towels
 Plastic Bag
 Agarose Gel
 Apron
 Goggles
Procedure:
1. Get gel made the day before, procedures explained the day they were made.
2. Place gel into gel box REMEMBER: Wells should be on the negative end.
3. Pour .25X buffer into gel box until gel is completely covered.
4. Carefully use the pipette to load 20l of each food color including the unknown into
wells of the gel. Keep the pipette steady so that you don't poke a hole through the
well. NOTE: Use a new pipette tip for each color.
5. Complete the diagram of your gel in the data section by indicating which color was
placed in the different wells using colored pencils. Record your unknown number.
6. Place lid on gel box.
7. Attach wires from gel box to power pack, making sure red wire goes into red slot and
black wire goes into black slot.
8. Turn power pack on.
9. Set voltage to 200V by pressing “V” side of V/A button and using up/down arrows
until reach 200.
10. Start running the gel by pressing the “run” button (running man).
11. Allow gel to run for 15 minutes.
12. Carefully remove gel.
13. Record data by completing a diagram of the resulting color bands in the gel.
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Data:
Hypothesis:
Unknown #: ________
1. Was your hypothesis supported or rejected? Explain.
2. What color pigments were in your unknown??
3. How does electrophoresis separate the dye pigments?
4. What charge is carried by the pigments in this separation? Support your answer.
5. Why might it be important to avoid contaminating DNA samples when doing a DNA
analysis?
6. If the samples were DNA instead of food color, what would be done now?
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