How is sickle cell anemia maintained in our world (why doesn't it eradicate itself)?
A person may have one sickle cell trait and not know it. If s/he mates with another person with this trait, their offspring will have the disease.
http://www.kidshealth.org/teen/diseases_conditions/genetic/sickle_cell_anemia.html
Sickle cell anemia is maintained in our world due to a phenomenon called "balanced polymorphism." To understand this concept, we need to delve into some genetics.
Sickle cell anemia is caused by a mutation in the hemoglobin gene that results in the production of abnormal hemoglobin proteins in red blood cells. This abnormal hemoglobin causes the red blood cells to become deformed and sickle-shaped, which can lead to various health problems.
However, carriers of the sickle cell trait, meaning individuals who have one copy of the mutated gene and one normal gene, show a unique advantage when it comes to survival in certain circumstances. In regions where malaria is prevalent, individuals with the sickle cell trait have increased resistance to the malaria parasite.
Malaria is a life-threatening disease caused by Plasmodium parasites that are transmitted through mosquito bites. The parasites invade red blood cells as part of their life cycle. In carriers of the sickle cell trait, the deformed shape of the red blood cells makes it difficult for the malaria parasites to thrive, thus reducing the severity of the infection.
As a result, individuals with the sickle cell trait have a survival advantage when exposed to malaria. They are less likely to die from severe malaria, which allows them to reproduce and pass on the sickle cell trait to their offspring.
So, the presence of sickle cell anemia in our world can be understood as a consequence of the selective advantage it offers against malaria. However, it is important to note that sickle cell anemia is still a serious condition that causes significant health problems, and efforts are made to prevent and treat this disease.