1. How is DNA evidence used in crime investigations?
Homework: Read and annotate article in Homework Packet 12

2. DNA Fingerprinting Each person’s DNA is unique
Sequencing someone’s DNA is like looking at their ‘biological fingerprint’
This has many applications
Crime solving, paternity, identifying individuals, cataloging endangered species

3. Steps of DNA fingerprinting
1. Collect sample of DNA
2. Cut DNA piece with restriction enzymes
3. Put fragments of DNA in a gel
4. Let gel run so fragments separate by size
5. Analyze the gel

4. Restriction Enzymes
Restriction enzymes are molecules that cut at specific DNA sequences
Ex: HidIII cuts between A and A (adenine and adenine)
They have a wide variety of uses in science
For DNA fingerprinting, they are used to create unique sized pieces of DNA
The way my DNA will ‘cut’ will be different from the way your DNA will ‘cut
This results in different sized pieces of DNA based on the individual

5. Steps of DNA Fingerprinting

6. What does the gel do?
The gel is the place where the DNA fragments are loaded
Each lane would contain different samples
The DNA fragments are exposed to an electrical current
DNA has an overall negative charge, so it moves toward the positive electric current

7. How do you analyze the gel?
The bigger pieces of DNA don’t move as far
The smaller pieces of DNA move further
Remember- every individual will have a unique set of DNA pieces, resulting in a unique pattern on the gel

8. DNA fingerprinting- complete the fingerprinting worksheet

9. Crime scene stories
On a separate sheet of paper you will create a crime scene story
Write a narrative that describes what happens that explains:
1. What the crime was
2. What evidence was left behind (hair, fingerprints, DNA, footprints etc.)
3. Three possible suspects and their story
4. Provide a sample DNA sequence from the suspect
You have 20 minutes to complete this! Make sure it is school appropriate or you will get a ZERO.

10. Solving a crime
Now, you will solve another group’s crime by conducting forensic analysis. On the back of their sheet of paper answer…
1. What analysis will you do on the various pieces of evidence?
2. Will you question the suspects before or after you have conducted DNA sequence? Why?
3. Explain the steps you take to sequence the DNA and compare it to the suspects.
4. How will you have the suspects DNA to compare it to?
5. Draw an example gel that confirms which suspect did it!
6. Do you think you have a solid case against the suspect? Why or why not? Can there be any errors in DNA fingerprinting?