disease. Dover, a pediatric hematologist and expert on fetal hemoglobin, initiated the use of the protein as a way to treat sickle cell anemia in adults. Medical implications The Hopkins-2 variant of hemoglobin has an oxygen affinity within the body, meaning that there is an increase of oxygen spreading through the body due to the fact that Ho-2 carries a higher amount of oxygen. There is no red cell effect with Ho-2 compared to Hemoglobin S, which changes the shape of the cell to become sickled. The Hopkins-2 variant of hemoglobin is not involved in forming sickle cells. There is a lack of phenotypic expression of Ho-2 in terms of sickle cell, so a person with sickle cell and hemoglobin Hopkins-2 would be asymptomatic. Genetic basis The Hopkins 2 variant of hemoglobin is the result of a mutation. Specifically, the mutated protein is composed of two alpha chains. The mutation for the Hopkins-2 variant of hemoglobin is located on the surface of the molecule. Within the Ho-2 variant, aspartic acid replaces histidine at position 112 on the alpha chain. Dr. Max Perutz examined the aspartic acid in alpha 112 claiming that the carboxyl group of the amino acid forms a hydrogen bond with phenolix hydroxyl, which in turn stabilizes the structure of the molecule and increases oxygen affinity. Ho-2 hemoglobin has high levels of oxygen, which replaces the lack of oxygen within red blood cells. Ho-2 is similar to Hemoglobin A, which is normal hemoglobin and also contains two α-chains. This provides an explanation as to how the Hopkins-2 variant of hemoglobin is related to the symptoms of sickle cell. Hopkins-2 can also interact specifically with Hemoglobin S. Hemoglobin S is the most common abnormal hemoglobin variant. Hemoglobin S is the variant that causes sickle cell, which is a disorder in which red blood cells break down and become abnormally shaped. Hemoglobin S has two beta chains, whereas hemoglobin Hopkins-2 has two alpha chains. Hopkins-2 makes up 22% of hemolysates in single heterozygotes; therefore, there is the normal version of the gene in these patients. Hemolysates are the products of the destruction of red blood cells. Ho-2 also comprises 11% of hemolysates in ‘double’ heterozygotes, which are when the gene contains both Hopkins-2 and Hemoglobin S. There are currently multiple possible explanations as to how the Hemoglobin variant Hopkins-2 works. One explanation that scientists have come up with is that