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Idea Transcript
Food dye electrophoresis
Student task sheet
Food dyes are attracted to the positively charged part of an electric field, just like DNA
Food dye electrophoresis You can do simple electrophoresis using food dyes, which are negatively charged molecules like DNA. Margarine or butter containers and batteries can be used to make simple electrophoresis kits. Alternatively, you can replace the batteries with four power packs connected in series. Go to: for this experiment.
Background activity: In this experiment the food dyes are placed in the wells in agar in the same way as samples of DNA when doing electrophoresis. Food dye molecules act as models for DNA molecules. This means they behave in a similar way to DNA during electrophoresis. Are they good models for DNA? •
Read the labels of the food dyes. Record their chemical names which are given as a number on the label. Convert this number to the chemical name of the food dye at:
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Check the size of the dye particles using paper chromatography. Are the food dye
Make a prediction: Which dye will move most during electrophoresis? Give a well-supported reason for this prediction.
Evaluation: (a) Summarise your results. How do they compare with your prediction? Explain any differences, if you can. (b) What variable did you use in making your prediction? (c) Other than size, the molecules could be different in other ways. Go to: for information about the molecules indexed by their chemical names. (d) How well do food dye molecules simulate the behaviour of DNA molecules during electrophoresis? Justify your answer.