The gamma globin genes (HBG1 and HBG2) are normally expressed in the fetal liver, spleen and bone marrow. Two gamma chains together with two alpha chains constitute fetal hemoglobin (HbF) which is normally replaced by adult hemoglobin (HbA) at birth. In some beta-thalassemias and related conditions, gamma chain production continues into adulthood. The two types of gamma chains differ at residue 136 where glycine is found in the G-gamma product (HBG2) and alanine is found in the A-gamma product (HBG1). The former is predominant at birth. The order of the genes in the beta-globin cluster is: 5'-epsilon -- gamma-G -- gamma-A -- delta -- beta--3'. HBG1 (Hemoglobin Subunit Gamma 1) is a Protein Coding gene. Diseases associated with HBG1 include Fetal Hemoglobin Quantitative Trait Locus 1 and Hereditary Persistence Of Fetal Hemoglobin-Beta-Thalassemia Syndrome. Among its related pathways are IL-2 Pathway and p70S6K Signaling. GO annotations related to this gene include iron ion binding and oxygen binding. An important paralog of this gene is HBG2.