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TECHNIQUES LAB C-2: CASTING & LOADING AN AGAROSE GEL
SEPARATION OF ASSORTED CHARGED DYES


Activity Sheet

Name_________________________________________
Date_______________ Period__________



PRELAB:
  1. Record your answers to questions a-c on the drawing of the electrophoresis gel box below.

    1. Label the gel, gel tray, and gel tray gates.

    2. Draw a line to show the desired buffer level. Label the line "buffer level".

    3. Use a large dot to show the dye placement. Label the dot "loading dye".


  2. Two dyes you must run are the xylene cyanole and bromphenol blue, which are in the "loading dye" we use to track the "invisible" DNA run in a gel. Predict whether they will migrate toward the anode or the cathode. Choose 4 other dyes, list them below and predict whether they will migrate toward the anode or the cathode.

    Xylene cyanole _______________________________________________________________________

    Bromphenol blue ______________________________________________________________________

    _____________________________________________________________________________________

    _____________________________________________________________________________________

    _____________________________________________________________________________________

    _____________________________________________________________________________________

    _____________________________________________________________________________________
OBSERVATIONS:
  1. Record the location of the loading dye(s) on the diagrams below.




  2. Label positive and negative ends of the gel in Figures A and B.

  3. Why would you want the wells to be in the center of the gel?

    _____________________________________________________________________________________


POST LAB:
  1. Based on your results, what do you conclude is the charge of each dye you ran?

    _____________________________________________________________________________________

    _____________________________________________________________________________________




  2. If the distance a dye travels is based only on size, which of your dyes is the largest? The smallest?

    _____________________________________________________________________________________

    _____________________________________________________________________________________




  3. From your data, what other conclusions could you make about the dyes?

    _____________________________________________________________________________________

    _____________________________________________________________________________________

    Note: Two dyes were combined to form "loading dye". One of these dyes moves faster than the small pieces of DNA, the other moves more slowly than the largest pieces of DNA.



  4. In this activity, DNA was not mixed with this loading dye. However, it will be when we need to separate fragments of DNA. Mark the "Fig. B Gel: after it has been run" drawing (above) to show where you would expect to find DNA.

Teacher Notes       Activity




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