*DNA FINGERPRINTING IS PARTICULARLY IMPORTANT IN CRIMINAL CASES BECAUSE IT PROTECTS THE INNOCENT AND HELPS IDENTIFY THE GUILTY.
OVERVIEW OF THE EXPERIMENT:
1. You will work in pairs. You will receive samples of four simulated DNA unknowns.
2. You and your partner will pour an agarose gel. The gel will have wells for loading the samples.
3. While your gel is hardening, you will add glycerol to the "unknown DNA" samples. Glycerol makes the samples dense enough to sink into the wells.
4. After the gel has hardened, it will be placed in the solution in the gel box. The "DNA" samples will be placed in the wells on the gel, and you will turn on the electrical current .
5. While the gel is running you will carefully compare the patterns of the known DNA's.
6. After 8 minutes, you will turn off the current, remove your gel and observe the patterns produced by your unknowns.
7. Finally you will compare the patterns on your gel to the known DNA patterns provided and draw conclusions about the identity of each unknown.
I. BACKGROUND
DNA "fingerprinting", like ordinary fingerprinting, makes use of a characteristic pattern that can be compared between individuals. What makes DNA "fingerprinting" special is that no fingers are required to do it, so an animal without fingers, a plant, or any other kind of living thing can be identified by its DNA fingerprint.
DNA is the code molecule that is found in every living cell and that tells cells what to do. Since every organism is a little bit different from every other (except for identical twins), the DNA instructions in one organism are different from those of others.
DNA is found in cells, so it is found throughout the body. DNA can be collected painlessly from blood, skin, or even hair. In the lab the DNA is cut at specific code sequences using special enzymes made by bacteria. The resulting pieces from different organisms vary in length just as the overall DNA’s vary. Finally, the DNA pieces are made to "line up" according to their length by a process called electrophoresis. The resulting pattern of "lines" lets scientists identify all organisms by their DNA, just as people are identifiable by the patterns on their fingertips.
The name electrophoresis means "to carry with an electric current." Electrophoresis is a process of moving molecules by attracting them to a electric charge that is opposite to their own charge. DNA has a negative charge, so it moves toward the positively charged electrode and away from the negatively charged electrode. The molecules are forced to travel through a Jell-O like substance placed between the oppositely charged electrodes. Larger pieces of DNA move more slowly than smaller pieces because larger pieces get tangled up more often in the web-like structure of the gel. The gel is made of agarose, a product made from seaweed.
PART A: FORENSIC SCIENCE - ASSAULT CASES
Assume that you are a molecular biologist involved in forensic medicine. Two women have been assaulted within a span of 2 weeks and you have been given the following evidence relating to the crime: Blood samples from both women, semen collected on each victim, and blood samples from three possible suspects.
You purify the DNA from each sample, cut the DNA’s with restriction enzyme and then perform agarose gel electrophoresis on the DNA as follows:
Well 1 -- Blood from victim A
Well 2 -- Blood from victim B
Well 3 -- Semen collected on victim A
Well 4 -- Semen collected on victim B
Well 5 -- Blood from suspect X
Well 6 -- Blood from suspect Y
Well 7 -- Blood from suspect Z
Results from the electrophoresis of DNA after cutting with
restriction enzyme: 
Questions:
1. A. Were both women assaulted by the same man? ______________________
B. Explain your reasoning.
2. A. Which, if any, suspect or suspects, is/are involved?
B. Explain your reasoning.
PRACTICE PART B: CONSERVATION SCIENCE - A PATERNITY CASE
Assume that you are a molecular biologist at a zoo. You are asked to help identify the biological father of a baby chimpanzee. After adding an appropriate restriction enzyme to each of the DNA samples, you perform agarose gel electrophoresis on the DNA.
Well 1: Sample from mother's blood
Well 2: Sample from baby’s blood
Well 3: Sample from blood of possible father E
Well 4: Sample from blood of possible father F
Well 5: Sample from blood of possible father G
Results from the electrophoresis of DNA after cutting with restriction enzyme:
Determine which DNA sample came from the blood from the child's actual father, and explain your findings.
GEL ELECTROPHORESIS AND DNA FINGERPRINTING LAB:
Version C
Supplies at a central location for use by the whole class:
65∞C water bath with flasks of melted agarose gel
Bottle of electrophoresis
solution
Check off the checklist of materials for the supplies at your station. A pair of students should work at each lab station.
Test tube rack
Four empty
1.5ml test tubes
Four 1.5ml
test tubes containing "DNA unknowns” "11", "12",
"13", "14"
1.5ml test
tube containing glycerol "G"
Micropipette
and tips
10ml graduated
pipette
Pro-pipette
3" X 2"
glass slide
Plastic "comb"
Plastic sandwich
bag
Marking pen
(Please use regular pen or pencil on paper.)
Small cup for
used tips
Electrophoresis
device ("gel box")
Transparent
plastic sheets for tracing staining pattern
Power supply
for gel boxes (Two lab stations will share one power supply.)
Procedure
I. Preparing the gel
A. Set glass slide on a
smooth, level section of lab bench where comb can be positioned over it later.
B. Fit the pro-pipette to the 10ml pipette and go to the flask of melted agarose gel; obtain 8ml of melted
agarose solution; return to your station and promptly empty the warm solution in the center of the glass
slide; place the comb
one centimeter from one end of the slide. 
C. Allow the agarose solution to cool and solidify for at least 3-4 minutes. While you wait for the solution
to cool, go on
to the next instruction. 
II. Preparing the samples for electrophoresis
A. Label the empty 1.5ml
test tubes with the numbers 11, 12, 13 and 14. 
B. Add samples of unknown DNA to your tubes as follows:
