Sequence of Action of Genes at the Secretor, H, ABO and Lewis Loci

It is argued that Lewis genes are responsible for adding specificity to glycoprotein molecules after the activities of the secretor, H and ABO genes, respectively, have been expressed. This conclusion is based on the results of studies on the expression of ABO and Lewis antigens in salivas from Australian aborigines, and on biochemical results. A simple figure illustrating the antigens determined on red cells and in body secretions as a result of the action of these genes, in their correct order--secretor, H, ABO, Lewis--is presented.