1. Most common blood types:
Forensic Serology
Blood
Most common blood types:
O Rh positive ---   39 percent O Rh negative ---   9 percent A Rh positive ---   31 percent
A Rh negative ---   6 percent B Rh positive ---    9 percent B Rh negative ---   2 percent AB Rh positive ---  3 percent AB Rh negative percent
Overall:
O 43% A 42% B 12% AB 3%

2. Blood
For years, doctors tried to transfuse blood from one patient to another
Their efforts ended in the patient’s body accepting the transfusion, or rejecting it
If rejected, the blood would coagulate, agglutinate, or clot, and the patient would die

3. Karl Landsteiner Discovered blood typing in 1901
Earned him the Nobel Prize 29 years later
He recognized that all human blood was not the same
Out of his work came the classification system we call the A-B-O system
Now docs had the key for properly matching the blood of a donor to the recipient
You cannot mix one blood type with another, if so there are disastrous consequences

4. Other Discoveries
1937 the Rh Factor was discovered (positive or negative blood)
Shortly after, numerous blood factors or groups were discovered
More than 100 different blood factors have been identified so far

5. Forensic Scientists
Until the early 1990’s, they would focus on blood factors for linking blood to an individual
They would do this because, in theory, no two people, unless identical twins, could have the same combination of blood factors
They are controlled genetically and are very distinctive in personal identification
Blood found at crime scenes can be identified by the factors and can thus link a suspect to the crime

6. DNA
Scientists no longer look for these factors, but characterize evidence by DNA, which carries the body’s genetic info
Dried blood and other biological evidence can be tested by this DNA technology
Where can you find DNA in blood?

7. Nature of Blood Blood is a mixture of:
Plasma: fluid portion of unclotted blood, made mostly of water, and accounts for 55% of the blood content
Suspended in the plasma are solids consisting of several cells- RBCs (erythrocytes), WBCs (leukocytes), and platelets. This accounts for 45% of blood content
Serum is the liquid that separates from blood when a clot is formed

8. Blood Components

9. Antigens
On the surface of each RBC, chemical structures called antigens, are found
The most important antigen systems are the A-B-O and Rh systems
If a person has A blood, then they have A antigens
B blood has B antigens
AB blood has both A and B antigens
O has no antigens
The presence of A and B antigens determines a person’s blood type

10. D Antigen Rh factor, or D antigen
If a person has the D antigen, they are Rh positive
If they lack it, then they are Rh negative
The presence or absence of three antigens-A, B, and D- must be determined in testing compatibility of the donor and recipient

11. Antibodies
Serum contains proteins called antibodies, which destroy a specific antigen
An antibody reacts only with its specific antigen and no other
Type A blood has A antigens, anti-B antibodies
Type B blood has B antigens, anti-A antibodies
Type AB has A and B antigens, no antibodies
Type O blood has no antigens, anti-A and anti-B antibodies

12. What would occur if…
It is only the antigen that will produce a response and bring on an attack
We transfuse type A blood into a type B patient?
This would cause…