Hemoglobin Gene Structure and Arrangement The human hemoglobins are encoded in two tightly linked structures: Alpha Gene Family: - Alpha gene cluster is encoded by genes located in chromosome 16 - The alpha gene cluster contains zeta gene that is expressed in the embryonic stage, the alpha-like genes that are not expressed (pseudogenes) Alpha genes that encode the alpha subunit of hemoglobin Beta Gene Family - The gene for the beta-globin chain is located on chromosome 11 - The beta gene cluster consists of the beta gene encodes for beta-subunit of adult hemoglobin two gamma genes (G γ and A γ ) that encode the γ chain of fetal hemoglobin the delta gene that codes for the subunit present in HbA2 Expression of Hemoglobin During Various Developmental Stages Embryonic Hemoglobin: Red blood cells first appear about six weeks after conception, these RBCs contain the embryonic hemoglobin synthesized by the yolk sac. These include Hb Portland ( ζ 2 γ ...