What causes sickle-cell disease?

Red blood cells contain a protein called haemoglobin which picks up oxygen from the air in the lungs and carries it around the body. People with sickle-cell disease have an altered form of haemoglobin, which tends to join together in long strands when it is not carrying oxygen. These strands of altered haemoglobin give the red blood cells their 'sickle' shape. Sickle-cell disease affects people who inherit two copies of the gene that makes the altered haemoglobin.

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A boy with sickle-cell disease learning about the inheritance of the condition.

How is sickle-cell disease inherited?

Sickle-cell disease affects people who inherit two copies of an altered gene from their carrier parents. Carrier parents have a one-in-four chance of having an affected child and a one-in-two chance of having a child who is an unaffected carrier. Carriers of sickle cell are not affected themselves, as they have a working gene as well as an altered gene.

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Inheritance of sickle-cell disease.

Why are sickle-cell carriers protected against 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.

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Carriers of sickle-cell disease are protected from the malaria parasite which is passed on by mosquitoes.

 

Principal Funder:

Wellcome trust

Major Sponsors:

GlaxoSmithKline life technologies