You have a slightly different enzyme than the A people, so you build a slightly different structure, and those of you that are AB have the enzyme from your mother, the other enzyme from your father, and now you make both of these structures in roughly equal proportions.
Su enzima es algo distinta de la del tipo A, por lo que la estructura es algo diferente, y aquellos que sean del tipo AB tienen una enzima de su madre, y la otra de su padre, y así sus estructuras están prácticamente balanceadas.