The IA allele encodes the A blood group antigen, IB allele encodes B, whereas, i encodes O blood group antigen.
Any substance that causes the body to make an immune response against foreign substance. Antigens include toxins, chemicals, bacteria, viruses etc that come from outside the body.
So we can conclude that the IA allele encodes the A blood group antigen, IB allele encodes B, whereas, i encodes O blood group antigen.
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