How can sickle cell anemia have a postive adaptive value (why would it be beneficial to have the disease)?
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Anonymous
ANSWERS: 2
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It grants resistance from malaria. malaria infects the red blood cells, and sickle cells provide some immunity from this.
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It is not beneficial to have Sickle Cell Anemia. It is a very painful disease. However, there is a reason why the HbS gene is selected for. Specifically, Sickle Cell Trait, when a person inherits one gene for normal hemoglobin (HbA) and one gene for sickle hemoglobin (HbS), affords a survival advantage, though not immunity or absolute protection, against malaria. People with Sickle Cell Trait do not exhibit any symptoms of Sickle Cell Anemia -- their hemoglobin is, for the most part, normal. Malaria is caused by the Plasmodium parasite which spends part of its life in the mosquito and the rest in the human host. The parasite invades the red blood and carries out its metabolic processes here. The presence of the parasite reduces oxygen tension in the cell -- when oxygen is reduced the cell will sickle. Because sickle cells are removed from the circulation, selective sickling of infected sickle trait red cells would reduce the parasite burden in people with sickle trait. These people would be more likely to survive acute malarial infections.
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