<prompt> Embryonic hemoglobin is:Alpha 2 Beta 2Alpha 2,Gamma 2Alpha 2 Delta 2Alpha 2  <response>: Normal mammalian hemoglobins contain two pairs of unlike polypeptide chains: one chain of each pair is or -like and the other is non- , , or . The -chains of all human hemoglobins encountered after early embryogenesis are the same. The non- chains include the -chain of normal adult hemoglobin Hb A , the -chain of fetal hemoglobin Hb F , and the -chain of Hb A2 Hb A2 , the minor component, which accounts for 2.5 percent of the hemoglobin of normal adults.The -chain of fetal hemoglobin Hb F differs from the -chain by 39 residues. Ref: Natarajan K., Townes T.M., Kutlar A. 2010. Chapter 48. Disorders of Hemoglobin Structure: Sickle Cell Anemia and Related Abnormalities. In J.T. Prchal, K. Kaushansky, M.A. Lichtman, T.J. Kipps, U. Seligsohn Eds, Williams Hematology, 8e. 