1: Preparation of Forensic Samples
For this lab exercise, it will be your job as part of Cuyamaca’s Forensics Investigation Team to determine
if there is sufficient evidence to charge one of the police department’s suspects with murder. The first
parts of the procedure for a have already been completed by another part of the Cuyamaca forensics
team. It will be your responsibility to run the final gel electrophoresis analysis to determine whether the
sample from any of the suspects matches the blood sample found at the crime scene.
The following samples and standards are available to be tested:
Standard: A HindIII DNA digest to be used as the size standard
CS: This is the sample from the crime scene.
S1: Suspect 1: Dr. Pete Moss
S2: Suspect 2: Dr. Forest Moss
S3: Suspect 3: Mr. Bud Wieser
S4: This is a blood sample from the victim, Dr. Dinah Soares
Each of the crime scene, suspect and the victim samples has already been prepared for analysis by the
Cuyamaca Forensics Investigation Team using the following procedure:1) Each blood sample was amplified using PCR (Polymerase Chain Reaction) to obtain sufficient DNA
for forensic analysis.
2) Ten microliters of each of the five samples was added to a clean tube and the tubes were labeled
according to the list shown above.
3) To each tube, 10 µl of an EcoR1/Pst1 restriction enzyme mix was added. All of the tubes were then
incubated at 37oC for 45 minutes.
4) The tubes were allowed to cool to room temperature, and 5 µl of loading dye was added to each tube.
These samples have now been delivered to you to complete the analysis of the DNA by
agarose gel electrophoresis. It will be your responsibility to set up and run the gel, and
then to analyze the results in order to determine whether if any of the three suspect’s
DNA matches the DNA found on the broken window at the crime scene.
Activity 2: Gel Electrophoresis of Forensic Samples
Preparation of Electrophoresis Gel
The electrophoresis equipment you will use to separate the DNA fragments into patterns that can be
compared is based on new technology that is somewhat different from the example you saw in the online
demonstration. The agarose gel is already prepared for you to use, and also contains the ethidium
bromide in the gel. This means that as soon as the gel has been run you will be able to view the results
by placing the gel on an ultraviolet (UV) illumination box.
In this lab exercise you will use the E-Gel®
electrophoresis system. It consists of a precast agarose gel which already contains
ethidium bromide (EtBr) and the EGel®PowerBase Question 1: Do you see any of the band patterns in the different lanes that appear to match
each other? Which lanes?
Question 2: Do any of the suspect samples appear to have recognition sites at the same
location as the DNA from the crime scene?
Question 3: Based on the analyses you have done, do any of the suspect samples of DNA
seem to be from the same individual as the DNA from the crime scene? Describe the scientific
evidence that supports your conclusion.
Activity 4: Summary of Data Analysis
In this activity, you will be summarizing your findings to the police department in order to determine
whether they have sufficient evidence for an arrest in the case. On the Skill Check worksheet, write a
summary of 3-4 paragraphs of your evidence, and who (if anyone) it points to as the alleged murderer. Be
sure to discus
Requirements: 33 | .doc file
