IGCSE Biology glossary
Sickle cell anaemia
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
A genetic blood disorder caused by a mutation in the gene for haemoglobin, resulting in abnormal sickle-shaped red blood cells. These rigid, crescent-shaped cells can block capillaries, reducing oxygen delivery to tissues and causing pain and fatigue.
What to include in an exam answer
Sickle cell is a co-dominance example: HbAHbA = normal, HbAHbS = sickle cell trait (carrier, some sickle cells), HbSHbS = sickle cell anaemia. Carriers (HbAHbS) have some resistance to malaria, which is why the allele persists in populations where malaria is common.
Example in context
Explain why the sickle cell allele is common in areas where malaria is prevalent (2 marks): Individuals who are heterozygous (carriers) have some resistance to malaria. They are more likely to survive and reproduce in malaria-endemic areas, passing the sickle cell allele to the next generation.
Related syllabus topic
Inheritance