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Blood grouping system

ABO blood grouping

The most common blood grouping system is the ABO blood grouping. Blood groups are classified depending on the presence or absence of A or B antigen on red blood cells. The resulting blood groups are A, B, AB, or O as shown in Figure 1.

Table of the different blood types and the molecules present in the blood of patients of each. In type A, red blood cells display A antigens on their surface, and there are antibodies against antigen B in the plasma. In type B, red blood cells display B antigens on their surface, and there are antibodies against antigen A in the plasma. In type AB red blood cells display A and B antigens on their surface, and there are no antibodies relating to antigens A or B in the plasma. In type O (also called zero or null), red blood cells do not display any antigens on their surface, and there are antibodies against antigens A and B in the plasma.

Figure 1: ABO blood grouping system

The genotypes and resulting phenotypes of each blood type are shown in the table below. Notice that the phenotype is decided by the dominant allele of the genotype. A and B are co-dominant, whereas O is recessive.

Phenotype (ABO) Genotype
A AA, AO
B BB, BO
AB AB
O OO

Rhesus group system

Besides the ABO system, the second most widely used blood system is the Rhesus (Rh) group system. The Rh status is typically denoted with a positive or negative sign after ABO type of a person. Positive relates to the presence of the Rhesus factor, or D antigen, and negative relates to the absence of this antigen.

Referred from:

Article
Blood transfusion
Article
Blood typing