What is coding? What type of interaction is observed between the IB and I0 genes that determine the human blood group? Between genes IA and IB?

Codomination involves the equivalent participation of both allelic genes in the formation of a trait in a heterozygous individual. In other words, when coding, heterozygotes fully manifest both allelic genes.
Genes IB (dominant) and I0 (recessive), which determine the human blood group, interact by the type of complete dominance. The dominant genes IA and IB interact by coding type. In a person with the IAIB genotype, both allelic genes fully perform their functions, therefore, red blood cells contain two antigens (A and B).

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