Gene ‘I’ has three different alleles ${{I}^{A}}$,${{I}^{B}}$,i.
-${{I}^{A}}$ produces A type of sugar / Antigen—> A group
-${{I}^{B}}$ produces B type of sugar / Antigen - B group
-i-No sugar - O group.
-Structure - Sugar polymers protrude from the surface of plasma membrane of RBCs.