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Genetic Markers in Blood

المؤلف:  Max M. Houck، Jay A. Siegel

المصدر:  Fundamentals of Forensic Science

الجزء والصفحة:  241

2026-07-29

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Genetic Markers in Blood

 A blood group is a class of antigens produced by allelic genes at one or more loci and inherited independently of other genes. Genetically controlled and invariant throughout a person’s life, blood groups are a robust biological marker. About 20 human blood groups are known to exist. The practical meaning of this is that a blood group is a permanent genetic trait—one that is controlled by genes and unchanging throughout a person’s life. This makes blood potentially excellent evidence for classification and possible inclusion or exclusion. Several systems are used to characterize and classify blood. The first and best known is the ABO blood group, discovered in 1900 by Karl Landsteiner. The letters A, B, and O refer to the antigens on the surface of the red blood cells; corresponding antibodies, anti-A and anti-B, are present in the plasma (www.nobel.se) (see Table 10.1). A person with Type B blood will have anti-A antibodies in his or her plasma. If the plasma is mixed with Type A blood, the cells will agglutinate, or clump together, from the reaction of the Type A antigens and the anti-A antibodies. Very few forensic laboratories currently perform blood group testing. If a stain is tested and is presumptively positive for blood, it is sent for DNA analysis (see “History: Landsteiner’s Breakthrough”).

Table 10.1 The Blood Groups in the ABO System and Their Antigens, Antibodies, and Frequency in the Population