Red blood cells carry antigens on their surfaces coded for by alleles of the gene designated by the letter I. IA is dominant to i and produces antigen A on the surface of red blood cells. The IB allele is also dominant to the i allele and produces antigen B on the surface of red blood cells. The i allele does not produce surface antigens. Use this information to label the possible genotypes of each blood type.

Allele IA produces antigen A

Allele IB produces antigen B

Allele i produces No antigen

To predict the genotype the main thing is that I is dominant to i allele.

So, the ABO grouping genotype should be like this.

Genotypes Phenotypes

IA IA A

IA i A

IB IB B

IB i B

IA IB AB

i i O

This the main ABO blood grouping genotyping and phenotyping used in transfusion medicine. And this is the most abundant test performed in the blood banks for transfusion of blood and record management.