Biology Question #3992

shane, a 10 year old male from doylestown asks on November 9, 2007,

How do scientists type your blood? How do they find out your blood type?

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The answer

Barry Shell answered on November 9, 2007

They take a sample of your blood and it only needs to be a drop or two from a pin prick. Blood types are determined by placing three very tiny drops of blood on a glass microscope slide. To one drop of blood, a drop of antibody solution to protein A (anti-A) is added. To the second drop, a drop of antibody solution to protein B is added. To the third drop, a drop of antibody solution to Rh factor (anti-Rh) is added. The blood drops and antibody drops are mixed and examined under a microscope for clumps of red blood cells, and the blood type is determined. Clumps mean that the particular protein (A, B, Rh) is present. For example, clumps in anti-A and anti-Rh, but not anti-B, would indicate a person with type A+ blood.

A protein is a type of very big molecule. An antibody is another type of protein molecule that sort of "fits" onto a particular type of other protein molecule. When the antibody fits on, it can cause a bunch of molecules to clump together. Basically, the antibody is a marker for the protein you are looking for. These are very very tiny things that sit on the outside of blood cells in your body. For more on this, check How Stuff Works (blood typing) and the Wikipedia entry on blood typing

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