Murder Mystery: DNA Fingerprinting Lab
Name: _____________________
Pre-Lab Activity Scene
A murder has occurred at the Ephrata Motel. At the time of the murder, the manager of the hotel
called the police right away. All individuals within the hotel were asked to donate a blood sample
for DNA fingerprinting. In addition, blood samples were “lifted” from the crime scene. Your
investigative team will do DNA fingerprints for three suspects to determine if one of them is the
murderer.
Materials
DNA Samples
Light Box
Agarose Gel
Micropippetors
Electrophoresis Chamber
Vortexer
Power Supply
Procedure
1. Form investigative teams with one other student. Each team pair will be responsible for
analyzing one set of DNA.
Lane 1: Crime Scene DNA
Lane 2: Victim’s DNA
Lane 3: Suspect #1 DNA
Lane 4: Suspect #2 DNA
Lane 5: Suspect #3 DNA
Lane 6: Suspect #4 DNA
Part I: Making the Agarose Gel
1. Seal the ends of the gel-casting tray with masking tape, and insert a well-forming comb.
2. Measure out 0.6g Agarose and put into 50mL Erlenmeyer flask. Add 30mL of 1X TBE Buffer.
3. Swirl the mixture and heat in microwave about 30 secs to boiling. The solution should be
more clear than before.
4. Pour the mixture to a depth that covers about 1/3 of the height of the teeth on the comb.
5. Allow the gel to solidify. This takes about 30 minutes.
Part II. PCR and Restriction Enzymes
Murder Mystery: DNA Fingerprinting Lab
The blood that was taken and found out the crime scene contained the entire DNA of all of the people
involved. We need to cut the DNA using restriction enzymes. Restriction enzymes look for a certain
pattern and cut the DNA into pieces. We will be using two restriction enzymes, EcoR1 and NoRo1.
EcoR1 recognizes …CGGC… and cuts between the Gs. The NoRo1 recognizes ….ATTA… and cuts
between the Ts. The restriction enzymes have been added and the DNA in the tubes is already cut.
Since only a small portion of DNA was available in the sample, we needed to amplify or “copy” the DNA
pieces we cut. This also was done using PCR. PCR using the enzyme polymerase to make more copies of
the DNA in the sample. So the tube on the table, has been cut and amplified. Ready to place onto the
gel.
Suspect 4
Suspect 3
Suspect 2
Suspect 1
Victim’s DNA
Crime Scene DNA
Part III. Gel Electrophoresis
1. Load the gel now with the various DNA samples. Make sure to put the correct DNA in the
correct lane on the gel. Add 10uL of each DNA sample, vortex each solution prior to taking
the sample. Do not mix solutions and use a new tip with each sample.
2. Place the gels into the chamber and pour 1x TBE buffer into the chamber just until it covers
the gel.
3. Close the chamber and attach the red(positive end) and the black(negative end) and do the
same with the power supply. Turn on the supply, set the voltage to 120 and hit start. Stop
the gel after 20-30 minutes or when the teacher directs you. Make sure your bands are
placed near the black end and will run to the positive end/red.
Murder Mystery: DNA Fingerprinting Lab
Part IV. Interpreting Results
1. Turn off power supply and remove gel from chamber. Place on paper towel. Then place gel on
white light box to interpret the banding pattern. Draw the bands you see on the Figure1A.
Part V. Discussion Questions
1. Compare all the DNA fingerprints. Can the guilty suspect be identified from the DNA
fingerprints? Which person do you think is the murder and explain your answer.
2. Discuss with your investigative team the potentially controversial aspects of DNA fingerprinting.
Write a summary of the key discussion points.
3. How might DNA fingerprinting be used to determine if a child belongs to a specific parent?
What might a child’s gel look like compared to a mother and father’s?
4. Using EcoR1, cut the DNA in samples A through C. How many segments will you end up with
after EcoR1? How many segments after NoRo1 will result?
a.) ATA CCG GCT ACC ATT AGG GCG GCT AC
b.) TAC GGC TAG CAT TAC GCT C
c.) ACT ACG GCT ACG ATT ACG A
Murder Mystery: DNA Fingerprinting Lab
Figure 1A
Lane 1
Crime
Scene DNA
Lane 2
Victim’s
DNA
Lane 3
Suspect 1
DNA
Lane 4
Suspect 2
DNA
Lane 5
Suspect 3
DNA
Lane 6
Suspect 4
DNA
Murder Mystery: DNA Fingerprinting Lab