0 or 1 of previous expression; also forces minimal matching when an expression might match several strings within a search string. \. Preceding one of the above, it makes it a literal instead of a special character. Preceding a special matching character, see below.
sickle cell disease. Sickle cell anemia, a common form of sickle cell disease, is caused by a particular mutation in the HBB gene. This mutation results in the production of an abnormal version of beta-globin called hemoglobin S or HbS. In this condition, hemoglobin S replaces both beta-globin subunits in hemoglobin.
Genetic Mutation. The gene that can cause Sickle Cell Anemia is called HBB and is located in Chromosome 11. HBB helps in the creation of hemoglobin in the body. A normal adult's hemoglobin consists of two alpha chains and two beta chains; HBB codes for the beta chain and the protein it synthesizes is called beta globin.he gene that can cause Sickle Cell Anemia is called HBB and is located in Chromosome 11. HBB helps in the creation of hemoglobin in the body. A normal adult's hemoglobin consists of two alpha chains and two beta chains; HBB codes for the beta chain and the protein it synthesizes is called beta globin.