-
As said before, sickle cell is caused by a mutation for gene for hemoglobin in red blood cells. People with sickle cell anemia have 2 mutated alleles while those with “sickle cell trait” have only one mutated allele and one normal allele.
The abnormal hemoglobin is “sticky” in low oxygen environments and causes red blood cells to become deformed and sickled in shape and rigid. This is a problem because these cells cannot pass though blood vessels as easily as normal RBCs can. I think (not sure on this one) that they can even get stuck and clog up vessels causing blindness and pain <span data-sheets-value=”{“1″:2,”2″:”https://19216801.onl/”}” data-sheets-userformat=”{“2″:268480,”9″:1,”10″:2,”14″:[null,2,1136076],”15″:”arial,sans,sans-serif”,”21″:1}”>https://19216801.onl/</span>.
The reason why so many black people have sickle cell, is that having the trait (so only one copy of the mutated allele) makes people more resistant to malaria <span data-sheets-value=”{“1″:2,”2″:”https://routerlogin.uno/”}” data-sheets-userformat=”{“2″:268512,”8”:{“1”:[{“1″:2,”2″:0,”5”:{“1”:0}},{“1″:0,”2″:0,”3”:3},{“1″:1,”2″:0,”4″:1}]},”9″:1,”10″:2,”14″:[null,2,1136076],”15″:”arial,sans,sans-serif”,”21″:1}”>https://routerlogin.uno/</span>. Malaria is a huge problem is sub-saharan Africa. While the exact mechanism is still unknown, we believe that this resistance is caused by RBC’s sickleing when infected by the malaia parasite. This makes people with sickle cell trait better able to survive than people without the trait in malaria prone regions.
So even though having sickle cell anemia makes people sick, having the sickle cell trait can be beneficial.
To be more precise, malaria doesn’t cause sickle cell anemia but it does make the disease more common. If you have one copy of the gene (allele) for sickle cell anemia and another healthy copy (heterozygous), you are more malaria resistant. Because of this, people that carry the gene are more likely to survive malaria than people with two healthy copies. Unfortunately, carrying two copies of the unhealthy allele (homozygous) has all of the bad effects you mentioned.
Higher rates of this unhealthy allele should be more common any where there is rampant malaria. Without malaria, there is no reason why people with one copy should survive better than people with two healthy copies (in fact, I believe there are some negative effects of carrying one copy).