Sickle-cell carriers and malaria
In the UK, about one-in-nine people of African or Afro-Caribbean descent is an unaffected carrier of sickle-cell. The number of carriers in these ethnic groups is probably so high because carrying the sickle-cell gene variant provided their ancestors with some protection from the disease malaria. When the malaria parasite invades the red blood cells of a sickle-cell carrier, the cells become 'sickle' shaped. These odd-shaped cells are then destroyed in the spleen, killing the parasite at the same time.