Summer Research Program for Science Teachers


Bibiane Petutschnig

South Shore High School




How can gel-electrophoresis help in the identification of a DNA sample?


£Students should understand the principles of gel electrophoresis.

o Standard C (Life Science)

o Standard B (Physical Science)

£Students should understand the applications of DNA testing.

o Standard E (Science and Technology)

o Standard F (Science in Personal and Social Perspectives)

£Students should be prepared for their hands on experience in the labs connected to this lesson (see lab-handouts)

o Standard A (Science as Inquiry)

£Students should become interested in presenting information with PowerPoint.

o Unifying Concepts and Processes


£Several packages of different flavors of Kool-Aid

£One bar-code that is cut from the back side of a Kool-Aid package containing cherry-flavor, there should only be one of the same flavor as the bar code in the collection of Kool-Aids.

£A computer or laptop with Power-Point installed

£A projector

£A white screen


The students are asked to imagine, that they own a cherry orchard. The Koolaid guys are siblings that live in the house next to theirs.




They should imagine, that one morning, they wake up and their cherries are gone. After a thorough investigation, only a piece of skin could be found on one of the cherry trees.


ASK: How can we find the culprit?

Can each Koolaid-guy be suspected of having committed the theft?


EXPECTED ANSWER: No, only the ones that contain cherries, pure or in a mixture with other flavors.


ASK: How can we find out which one of those did it?


The students should be reminded at this point, that the DNA that is contained in the cells of the skin is characteristic for the individual that the tissue stems from.


If we can find a way to process the DNA of the skin that was found and compare it to the DNA of the suspects, we will be able to identify the Koolaid-guy, who did it.




The teacher should point out the analogy between the pattern that you can see in an electrophoresis gel and a bar code that is used to identify products by a scanner in a supermarket.


Compare the cut out bar code to the bar code that you find on the back of the Koolaid packages. There should be only one match. You have identified the culprit!


Living Environment Lab #1: How do I prepare DNA-fragments and an agarose-gel for gel-electrophoresis?

Living Environment Lab #2: How do I perform gel electrophoresis?


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