is seizing the opportunity not only to fund-raise but also to educate the public about the disease.

*** SICKLE CELL ABNORMALITY What it is: Sickle cell is an inherited change in the blood. The protein haemoglobin, which is responsible for the red colour of blood, is made slightly differently in this disease. Normal adult haemoglobin (HbA) is replaced by abnormal sickle haemoglobin (HbS). Haemoglobin is used to carry oxygen in the body, but when HbS gives up its oxygen, its units stick together, forming long chains which change the shape of red blood cells from their normal flat shape to a long, pointed shape like a sickle or scythe.

*** Who gets it: It is inherited from one's parents. Inheriting the sickle cell gene from one parent and the gene for normal HbA from the other produces the sickle cell trait, which is harmless and cannot become the disease. Inheriting the HbS gene from both parents, on the other hand, results in sickle cell SS disease.

*** Whom it affects: Mostly people of African origin. The abnormality also occurs in people from Central India, Saudi Arabia and the Mediterranean area.

Positive or negative? A blood test called haemoglobin electrophoresis indicates whether or not an individual has sickle cell anaemia. A sickle or solubility test will detect HbS but will not distinguish the sickle cell trait from the full-blown disease.

*** SICKLE CELL TRAIT What it is: The harmless carrier state for abnormal sickle haemoglobin (HbS) gene.

Who gets it: Inherited from one parent.

Does it cause problems? Only rarely. Red blood cells in the sickle cell trait normally do not contain enough HbS to cause sickling. Conditions in the kidney are especially favourable for sickling, and small areas of damage can sometimes lead to blood in the urine. People with the trait may also develop problems when exposed to low oxygen levels, such as respiratory depression following alcohol, drugs or anaesthesia, prolonged breath-holding, or climbing at high altitude.

Inheriting the disease: Sickle cell trait can be passed on to progeny. If both partners have the cell trait themselves, there's a four in one chance at each pregnancy the gene will be inherited from both parents and the child will have the disease. Couples having the trait should both be tested to determine whether their child(ren) may be affected.