Phenotypes and Genotypes

A phenotype consists of only those traits or antigens that can be directly typed, whereas a genotype is the sum of all genes a person has inherited within a blood group system.

Table 4-5 shows ABO phenotypes and possible genotypes if only O, A, and B genes are considered.

Table 4-5. Correlation of ABO phenotypes and genotypes.

Phenotype Possible Genotype
A AA or AO
B BB or BO
AB AB
O OO

However, if A1 and A2 subgroups are considered, the phenotypes and genotypes of group A are expanded (Table 4-6).

Table 4-6. Possible genotypes of A1 and A2 subgroups.

Phenotype Possible Genotype
A1 A1A1 or A1O or A1A2
A2 A2A2 or A2O

Note: The A1 and A2 phenotypes are denoted by using subscripts. Genotypes are denoted by using superscripts.

Phenotypes and Genotypes