ABO Blood Group System (Cont)

 

  • The red cell antigens are the phenotypic expression of inherited genes.
  • The genes are co-dominant, so each gene contributes to the same extent in the antigenic effect.
  • The A gene produces the A phenotype, the B gene produces the B phenotype while the O gene results in no effective antigens. Thus there are six possible genotypes but only 4 phenotypes:
 
Phenotypes Genotypes
O
OO
A
AA or AO
B
BB or BO
AB
AB

 
Phenotypes Population Frequency
O
47%
A
41%
B
9%
AB
3%