Dna Fingerprinting Lab Report 11-15-12 6a122p

“Using DNA Fingerprinting to Solve Crimes and Other Mysteries” Calista Miller November 15, 2012 Partners: Maeve Geraghty, Dane Schatz, Aaron Spira

Introduction: In this lab, our group tested to see which suspect’s DNA matched that of the crime scene. Our hypothesis was: If the distance a DNA fragment travels is affected by the source, then changing the source changes how far the fragments travel. The independent variable is the source of the DNA. The dependent variable is the distance the DNA fragments travel. The controlled variables are the agarose gel, the 200 volts of electricity, the well, the micropipetter, the buffer, and the DNA fast-blast staining. Materials and Methods: Materials 

1 Agarose Gel

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Micropipetter

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20 micro liters of DNA (for each)

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DNA fast blast stain

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Electrophoresis Chamber

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Buffer

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Power Supply

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Different sources of DNA

Procedure First, the gel was placed in the little electric box. Then, buffer was poured into the electrophoresis chamber until the gel was slightly immersed. At that point, the DNA was

taken by the micropipetter, then slowly lowered above the well and deposited. This was repeated for each container of DNA (2 CS, 2 S1, and 2 S2). The cover was then put on the electrophoresis chamber and was hooked up to electricity feeding wires which directed 200 volts of DNA into the electrophoresis chamber with the DNA. Staining- The gel was immersed in 10% solution of DNA Fast Blast stain for 2 minutes. Then after removing gel from stain, it was immersed in warm water for 1 minute to begin de-staining the gel. Next, the gel was transferred to a second warm water bath for 2 minutes and to a final warm water bath for 5 minutes. Gel was then stored for 4 days in a dark drawer before recording the final results.

Results: We observed and measured the distance the DNA fragments traveled. The DNA from the crime scene had 4 fragments that moved 27, 28, 36, and 40mm, as did the DNA from Suspect 2. Yet the DNA from Suspect 1 only had 2 fragments with the measurements of 27.5 and 35mm. Suspect 2 is the person who was at the scene because the DNA matches. So it did show that if DNA came from a different source its fragments would travel different distances. My group’s hypothesis was ed. Conclusion: So, the DNA ed our hypothesis of: “If the distance a DNA fragment travels is affected by the source, then changing the source changes how far the fragments travel.” We observed and measured that the DNA from the Crime Scene matched that of

Suspect 2, proving that Suspect 2 has been at the scene of the crime before. So the source of the DNA does affect the distance the DNA fragments travel.

Discussion: My group did not encounter any pitfalls, but possible pitfalls when conducting this experiment are: inserting the micropipetter too deeply into the well and poking a hole in the gel causing the DNA to spill over into other wells, inserting the micropipetter to high and the DNA spills onto the gel, putting the agarose gel facing toward to opposite side causing the DNA to come out the top of the well when the electricity is turned on, and staining the gel improperly and the DNA is no longer visible. One thing my group could have done to make this a better lab was test it more, because in real crime labs, they test the DNA 10 or more times before they give an answer and not just one. Overall, it was a successful lab.