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Blood is classified into different groups according to the presence or absence of molecules called antigens on the surface of every red blood cell in a person's body. Antigens determine blood type and can either be proteins or complexes of sugar molecules (polysaccharides). The genes in the blood group antigen family provide instructions for making antigen proteins. Blood group antigen proteins serve a variety of functions within the cell membrane of red blood cells. These protein functions include transporting other proteins and molecules into and out of the cell, maintaining cell structure, attaching to other cells and molecules, and participating in chemical reactions.
Blood group antigens play a role in recognizing foreign cells in the bloodstream. For example, if a person with blood type A receives a blood transfusion with blood type B, the recipient's immune system will recognize the type B cells as foreign and mount an immune response. Antibodies against type B blood cells (anti-B antibodies) are made, which attack and destroy the type B blood cells. This sort of blood type mismatch can lead to illness. Some blood types are associated with more severe immune reactions than others. The blood type of donated cells, or tissues in the case of organ donation, is checked before being given to a recipient in order to prevent this immune response.
There are 29 recognized blood groups, most involving only one gene. Variations (polymorphisms) within the genes that determine blood group give rise to the different antigens for a particular blood group protein. For example, changes in a few DNA building blocks (nucleotides) in the ABO gene give rise to the A, B, and O blood types of the ABO blood group. The changes that occur in the genes that determine blood group typically affect only blood type and are not associated with adverse health conditions, although exceptions do occur.
The HUGO Gene Nomenclature Committee (HGNC) provides an index of gene families (http://www.genenames.org/cgi-bin/genefamilies/) and their member genes.
Genetics Home Reference summarizes the normal function and health implications of these members of the blood group gene family: SLC4A1 and XK.
Genetics Home Reference includes these conditions related to genes in the blood group gene family:
You may find the following resources about the blood group gene family helpful.
anion ; antigens ; carrier ; cell ; cell membrane ; DNA ; gene ; immune response ; immune system ; polysaccharides ; protein ; red blood cell ; solute
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
These sources were used to develop the Genetics Home Reference summary for the blood group gene family.
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.