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.
Sickle cell anemia is caused by a mutation in the gene that tells your body to make hemoglobin â the red, iron-rich compound that gives blood its red color. Hemoglobin allows red blood cells to carry oxygen from your lungs to all parts of your body.In sickle cell anemia, the abnormal hemoglobin causes red blood cells to become rigid, sticky and misshapen.The sickle cell gene is passed from generation to generation in a pattern of inheritance called autosomal recessive inheritance.emoglobin allows red blood cells to carry oxygen from your lungs to all parts of your body. In sickle cell anemia, the abnormal hemoglobin causes red blood cells to become rigid, sticky and misshapen.