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.
Causes of sickle cell anaemia. Sickle cell anaemia is caused by a genetic mutation that affects the normal development of haemoglobin. A genetic mutation is a permanent change in the normal pattern of genetic information inside all living cells.This results in one or more of the body's processes not working properly.auses of sickle cell anaemia. Sickle cell anaemia is caused by a genetic mutation that affects the normal development of haemoglobin. A genetic mutation is a permanent change in the normal pattern of genetic information inside all living cells.