aim: how is blood type determined? do now: 1.how are blood types determined by investigators? 2.in...

Aim: How is blood type determined?

Do Now:

1.How are blood types determined by investigators?

2.In detail explain what would happen if a person with blood type A received a transfusion from blood type B?

3.What would happen if a person who is Rh- received a transfusion from Rh+?

HW: questions 9 and 10 on page 329

Thursday 4/16/15

1. If a person has O - blood, which blood types can they receive?

2. If a person has A+ blood, which blood types can they receive?

Friday 4/16/15

• AIM: how are blood stains analyzed?

• DO NOW:

Scenario: You are an investigator who comes across this mark on the wall. What

should you find out?

• Is it blood?• Is it human blood?• Who does it belong to?

– Determine blood type, alcohol content, drugs present– Determine the method(s) in which blood may have been deposited

Blood Evidence• Bloodstains may look like purple paint, grease

stains, ketchup stains, and many other things besides blood.

A.

B. Presumptive Tests for Blood Determination

1. Kastle-Meyer (KM)color test—– a mixture of

phenolphthalein and hydrogen peroxide

– the hemoglobin will cause the formation of a deep pink color if blood is present

– https://www.youtube.com/watch?v=c2C-AveVMw0

2. Hematest tablet—reacts with the heme group in blood, causing a blue-green color

https://www.youtube.com/watch?v=RrNUAXcMeus

Hemastix Test - YouTube

3. Luminol - C8H7O3N3

• Chemical that reveals invisible blood traces

• Glows blue in the dark• Capable of detecting

bloodstains diluted up to 300,000 times

• Detects Iron in Hemoglobin

• Won’t affect DNA testing

Luminescence

How does luminol work?

The hydrogen peroxide and the luminol are actually the principle players in the chemical reaction, but in order to produce a strong glow, they need a catalyst to accelerate the process. The mixture is actually detecting the presence of such a catalyst, in this case the iron in hemoglobin

C. Confirmatory Blood Tests

• Antibody & Antigen Reaction

*In ABO Groups clotting occurs if the antigen comes in contact w/ same antibody type.

Animal BloodLarger nucleic red blood cells

Frog blood

Numerous non-nucleic red blood cells--5 to 6 million per mm3Larger but less numerous white blood cells 5 to 10,000 per mm3

600:1 ratio

Human Blood

1. Human versus Animal Blooda. Microscopic observation

Is it human or animal blood?• Precipitin test: uses an

animal serum that contains specific antibodies specific to human antigens– Agglutinates human

blood

• Sensitive test• Can use diluted blood• Works on old blood

b. Precipitin test—

• Rabbits make antibodies against human blood.

• If human blood is added to this rabbit serum a precipitate will form.

Where is the precipitate and why did it form?

Humanblood

HumanAntiserum

from rabbit blood

2. Blood Typing

a. Blood type A – antigen A on the surface of the cell

and – will agglutinate with blood type B

which makes Ant-A.

b. Blood type B– antigen B on the surface of the cell– will agglutinate with blood type A

which makes Anti-B.

c. Blood type AB– antigens A and B on the surface of

the cells– Will agglutinate with both type A or

type B blood.

d. Blood type O– neither antigen A nor B– will not agglutinate.

• Illustration of the forward and reverse grouping reaction patterns of the ABO groups using a blood group tile

http://www.bh.rmit.edu.au/mls/subjects/abo/resources/genetics1.htm

Once you determine it is human…

• How do we individualize?

Summary• When an investigator comes upon a red mark at

a crime scene what are 3 questions that he needs answered about the stain.

• List 2 tests that are used to determine if a red mark is blood

• Describe one of these tests in detail.

• List 1 test used to determine if the blood stain is human blood.