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Published bySarah Stephens Modified over 9 years ago
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BLOOD TYPING
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BLOOD EVIDENCE Blood typing is class evidence. It does not prove guilt because many people share the same blood type. However, it can exclude a suspect. In the early 1900’s Karl Landsteiner discovered that peoples blood did not always mix freely. The presence or absence of particular proteins found in the cell or within the plasma membrane of red blood cells determines a person’s blood type. An antibody reaction test is used to determine the blood type.
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42% 12% 3% 43% of the population in the United States
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A AND B PROTEINS A and B proteins are found on the surface of red blood cells. If a person contains the A protein, then they will have Type A blood. If a person contains the B protein, then they will have Type B blood. If a person has both the A and B protein, then they will have Type AB blood. If a person does not have either blood protein, then they will have Type O blood.
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RH FACTOR Alexander Weiner (1940) found another type of blood protein while working with Rhesus monkeys. This is known as the Rh factor. 85% of the human population has this blood protein. If you have this protein the Rh factor is designated as Rh+. If you do not have this protein the Rh factor is designated as Rh- Therefore, a person’s blood type is based on whether or not they have the A, B and Rh proteins.
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ANTIBODIES B-lymphocytes (a type of white blood cell) secrete antibodies. These antibodies are Y-shaped and bind to the molecular shape of antigens (foreign invaders). The antibodies recognize the antigens as a foreign substance. The antibodies and antigens fit like puzzle pieces.
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ANTIGEN-ANTIBODY RESPONSE The antigen-antibody response-is when a foreign invader is recognized by the immune system. Explanation: If a person with blood type B is given a blood transfusion with blood type A then foreign type A antigens alerts the immune system. Our body responds in two ways: 1. A lymphocyte makes specific antibodies against that protein.
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These will be Y-shaped and have a specific binding site that attach to the A protein. 2. Another white blood cell called a phagocyte will be released to engulf the invader. Remember Antigens determine your blood type. Ex: If you have blood type A you will have anti-B antibodies. Terminology: Agglutinogens are antigens Agglutinins are antibodies.
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BLOOD TYPE CHART Blood Type Can Give Blood To Can Receive Blood From AA, ABO, A BB, ABO, B AB O, A, B, AB O O
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