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Gene · Blood
HBB
Haemoglobin subunit beta — Encodes the beta chain of adult haemoglobin; a single-letter change in it causes sickle cell disease, and reduced output causes beta thalassemia.
11p15.4bloodsickle cellthalassemia
Schematic only — arm proportions are approximate and band detail is not drawn to scale. Cytogenetic location as published by NCBI Gene.
What this gene does
HBB is the recipe for one of the two protein chains that make up adult haemoglobin, the molecule that carries oxygen in your blood. Change one letter of the recipe and the protein sticks to itself, causing sickle cell disease. Make too little of it and you get beta thalassemia. One gene, two very different diseases, depending on how it goes wrong.
HBB, at 11p15.4, encodes haemoglobin subunit beta. The p.Glu6Val variant (rs334) produces haemoglobin S, which polymerises when deoxygenated. Over 300 HBB variants reduce or abolish beta-globin synthesis, causing beta thalassemia. Approved editing therapy does not target HBB itself but the BCL11A enhancer, reactivating fetal haemoglobin as a functional substitute.
Sources
MedlinePlus Genetics, U.S. National Library of Medicine HBB gene ↗
Written by The CRISPR Atlas editorial teamLast updated Aug 19, 2026
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