Sickle Cell Anaemia

Question 1

Incidence

Answer 1

10-30% equatorial Africa

Question 2

What is the underlying genetic abnormality responsible for sickle cell disease, and how does this lead to sickling?

Answer 2

Normally, hemoglobin A (HbA), which makes up most normal adult hemoglobin (96%–98%), is composed of two alpha-globin and two beta-globin chains. However, HbS possesses one abnormal beta-globin chain because of a single valine substitution for glutamic acid at the sixth position of the beta-globin chain.

Answer 3

The homozygous genotype HbSS (i.e., two abnormal beta-globin chains) results in SCD, with the potential for hemolysis and its resultant complications.
• The heterozygous carrier state HbAS (i.e., one abnormal and one normal beta-globin tourniquets be avoided? gene) is called sickle cell trait. This genetic makeup of sickle cell trait may confer protection to individuals exposed to the malaria-causing parasite Plasmodium falciparum.