Structure and Genetics
Most types of normal hemoglobin, including hemoglobin A, hemoglobin A2, and hemoglobin F, are tetramers composed of four protein subunits and four heme prosthetic groups. Whereas adult hemoglobin is composed of two alpha and two beta subunits, fetal hemoglobin is composed of two alpha and two gamma subunits, commonly denoted as α2γ2. Because of its presence in fetal hemoglobin, the gamma subunit is commonly called the "fetal" hemoglobin subunit.
In humans, each chromosome 11 contains two similar copies of the gene that encodes the gamma subunit, γG (glycine as residue 136) and γA (alanine as residue 136). (The beta subunit is also on Chromosome 11) The gene that codes for the alpha subunit is located on chromosome 16 and is also present in duplicate.
Read more about this topic: Fetal Hemoglobin
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