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.
As, for example, sickle cell anemia, which is a serious disease occurs due to mutation from single base substitution. A point mutation of the Î²- globin gene in codon 6 results in the substitution of glutamic acid by valinethereby causing sickle cell anemia. Î²-globin is an important component of haemoglobin (HbA).