Blood Typing
In 1901, Austrian scientist Karl Landsteiner discovered blood types. He noticed that blood clumping often occurred when he mixed blood
from two different sources together, and he determined that this clumping was a result of an immunological response.
Landsteiner's experiments, with contributions from Jan Jansky, ultimately revealed the four major blood types possible in humans. In 1930, he was
awarded the Nobel Prize in Physiology or Medicine for this work. The four blood types A, B, AB, and O were differentiated based
on the presence or absence of certain proteins called
antigens
on the red blood cell surface.
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Type A blood has A antigens.
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Type B blood has B antigens.
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Type AB blood has both A and B antigens.
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Type O blood has no antigens.
Identification of these blood types was a significant medical development, as it provided doctors the
ability to more successfully perform blood transfusions with compatible blood. Blood antigens that are different from those normally
found in a transfusion recipient's bloodstream are bound by antibodies and stimulate an immune response. Scientists quickly
realized that patients with type AB blood were able to receive transfusions from all blood types and those with type
O blood were able to donate blood to all blood types.
Upon his blood typing discovery, Landsteiner realized that blood types were inherited from one's parents. Scientists determined
that a child's blood type was dependent upon the blood types of his or her parents. Below is a table of the blood type possibilities
for a child based on his or her parents' types.
In the 1920s, scientists began using blood typing as a technique for determining paternity and maternity. However, due to the
low number of possible blood types many alleged fathers were falsely included by matching children that were not theirs. Using blood
typing as a tool for paternity testing, the
power of exclusion
was only 30%.
With the discoveries of
Rh types
and rare genetic variations such as the Bombay phenotype,
blood typing was quickly ruled an unreliable paternity testing technique.
(1900s) Blood Typing
(1930s) Serological Testing
(1970s) HLA Typing
(1980s and 1990s) RFLP Technique
(1990s) PCR Technique
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