Sc 9
Forensic Unit
1
Blood Analysis
There are four types of human blood: A, B, AB and O. The most common type is O (46%
of Canadians have this type). A person’s blood type can be determined by adding antiserum to it. When anti-A is added to type A blood clotting occurs. The same is true of
anti-B and type B blood. Both anti-A and anti-B cause clotting in type AB blood. No
coagulation occurs in type O blood.
type A blood
anti-A
anti-B
type B blood
coagulation
type AB blood
type O blood
coagulation
coagulation
coagulation
Objective:
To determine the blood type of the thief (found on the broken glass).
Spot Plate
Materials:
simulations of type A, B, AB and O blood
simulations of anti-A and anti-B
spot plate
Method:
1. Stir the simulated blood types and antiserums before beginning your experiments.
DO NOT MIX UP THE EYEDROPPERS!
2. Clean and dry your spot plate before beginning to be sure that you will not
get incorrect results due to contamination left on the plate!
3. To see what a positive test for each blood type looks like, complete a series of
tests on your spot plates. Organize your tests as follows:
a. Add Blood Type A to the First two cups in Column one.
b. Add Blood Type B to the First two cups in Column two.
c. Add Blood Type AB to the First two cups in Column three
d. Add Blood Type O to the First two cups in Column four.
Sc 9
Forensic Unit
2
3. Now add the antiserum to note what happens for each of the blood
types.
a. Add 3 drops of ANTISERUM A to each blood type in Row 1
b. Add 3 drops of ANTI SERUM B to each blood type in Row 2
c. gently swirl for about 30 seconds
d. carefully observe around the edges for clumping (you may have to wait
for about 3 minutes to distinguish between some samples). COLOUR the
circle on the diagram above to indicate where coagulation (clumping)
occurred.
Now you will use these examples to determine the Blood type of the unknown
sample from the “crime scene.
4. Using two clean cups from the same spot plate, test the unknown blood sample
from the crime scene. Use the same method you used to test the known samples.
Compare your results with those that are known.
5. WHAT TYPE OF BLOOD WAS COLLECTED FROM the CRIME
SCENE?
6. Thoroughly wash and dry the spot plate when finished, and return the
“blood” and “antiserums”.
Sc 9
Forensic Unit
7.
For The TEACHER:
8. Blood Typing:
Type A = BaNO3 0.25M + congo red
Type B = NaCO3 -.5 M + congo red
Type AB = AgNO3 0.1 M + PbNO3 0.1M + RED FOOD DYE (congo red reacts)
Type O = H2O + Congo Red
Anti A = NaSO4 0.1 M
Anti B = CaCl2 0.5 M
3