Hemoglobin A2 (HbA₂) is a normal variant of

hemoglobin A Hemoglobin A (HbA), also known as adult hemoglobin, hemoglobin A1 or α2β2, is the most common human hemoglobin tetramer, accounting for over 97% of the total red blood cell hemoglobin. Hemoglobin is an oxygen-binding protein, found in erythrocyte ...

that consists of two alpha and two delta chains (α₂δ₂) and is found at low levels in normal human

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

. Hemoglobin A2 may be increased in

beta thalassemia Beta thalassemias (β thalassemias) are a group of inherited blood disorders. They are forms of thalassemia caused by reduced or absent synthesis of the beta chains of hemoglobin that result in variable outcomes ranging from severe anemia to cli ...

or in people who are

heterozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mo ...

for the beta thalassemia gene. HbA2 exists in small amounts in all adult humans (1.5-3.1% of all hemoglobin molecules) and is approximately normal in people with

sickle-cell disease Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red blo ...

. Its biological importance is not yet known.

References

External links

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Hemoglobin A2 - The clinical significance
Hemoglobins {{protein-stub