BY: KHIZRA YOUNISBRITTANY ALDARONDO

ALEJANDRO REYESKEVIN MAC

Precipitin Test

Precipitin Test: How it is used

The Precipitin test is used to help distinguish human blood from a possible animal blood.

Every creature creates protein and if another type of protein is introduced in the system then the creature’s body will not accept the proteins.

The body will create antibodies for the foreign proteins, investors take these antibodies out.

Precipitin Test: How it is used

The serum taken will have the antibodies that react to human antigen when human blood is added to the serum.

When the human blood is added to that serum then it will precipitate if the blood is actually human.

Diagram

Visual of the Precipitin Test

Strengths

The precipitin test is sensitive and will work on small traces of blood.

It determines whether the blood is from a human or animal.

It is easy to tell if it originated from a human from the results.

It takes about 24-48 hours

Weaknesses

The precipitin requires antisera which is found in rabbits.

Humans have different size veins meaning that it can be difficult drawing blood.

The conditions that the test undergo are precise from the temperature of the reaction and the timing.

There has to be an optimal concentration of both antigen and antibody.

Cases

On Saturday morning, Mr. Lee went to go drop off his dog at his pet day care. But something didn't feel right when he entered. All the dogs were barking and seemed to be irritated, which was very unusual.

There was a new person at the front desk, and when Mr. Lee asked for the regular receptionist, the man replied in an agitated voice. Mr. Lee asked to use the bathroom and as he was walking down the hallway, he saw bloodstains on one side of the wall.

Cases (continued)

He went back home immediately and called the police and told them what he saw. The police came to investigate and there they found traces of blood.

Unable to determine whose blood it was, they took the Precipitin test and realized it was human blood, not animal.

Originally, they had thought that a dog might have been killed there. However, it turned out that the receptionist had gotten into an argument with her boss and he had a very short temper.

Review Questions

1. What animal is mostly used in the precipitin test?

2. What is the main purpose of the Precipitin test?

3. What did Mr. Lee see in the hallway that made him call the police?

4. Will the Precipitin test work on small traces of blood?

5. Is this test sensitive?

Cited Sources

http://www.siracd.com/life/life_case2.shtml http://www.fmap.archives.gla.ac.uk/Case%20Files/Bloodtest/Bloodte

st.htm http://meaganpickles.tripod.com/forensicbiology101/id8.html http://www.forensicsciencecentral.co.uk/biology.shtml http://www.slideshare.net/rubina1000/precipitin-protocol http://classes.midlandstech.edu/carterp/Courses/bio225/chap18/

figure_18_03_labeled.jpg http://classes.midlandstech.com/carterp/Courses/bio225/chap18/18-

03_Precipitin_1.jpg