Why is sickle cell anemia most common in black individuals?

Answer 1

Sickle-cell anemia is caused by a defective gene that produces an abnormal form of hemoglobin which is called hemoglobin S. And this gene is particularly common in Western Africa and people of Western African Ancestry. An estimated 8 to 12 percent of all African Americans carry the sickle-cell gene.

Answer 2

Long explanation, for the short version skip to the last paragraph:

To answer this question one must understand the pathophysiology, genetics and subsequent effects of sickle cell. This is a genetic disease in which there is a defect in the synthesis of hemoglobin, which is present in our red blood cells (RBCs) and functions to transport oxygen from our lungs to the rest of our body. (The specific defect, for this of you who are interested, is the replacement of a negatively charged glutamic acid with a neutral valine) Because of this defect in hemoglobin, the RBCs of this with sickle cell are misshapen. The most striking consequence of this is that the abnormally shaped RBCs have trouble making it through the tiniest of blood vessels (capillaries), thus clogging them and resulting in loss of blood flow and oxygen delivery to downstream tissues (known to doctors as a vasooclussive crisis).

A person can fall into 3 categories with regards to sickle cell: affected, unaffected or carrier. An affected person has 2 copies of the bad gene, an unaffected person has no copies, while a carrier has only 1 copy of the bad gene. An affected person will likely have a severe form of the disease, and experience many painful and debilitating episodes of vasooclusion and possibly an early death. Someone who is a carrier will have a milder form of the disease with fewer/less debilitating symptoms.

A fortuitous side effect of sickle cell is that because the RBCs are misshapen, they are less suitable for infection by organisms which would normally reside within them, the most significant of these being malaria. An affected patient is protected against malaria, but has such a severe form of the disease that he/she will likely die an early death. A carrier is also protected from malaria, and because they don't suffer the same severe effects of sickle cell as an affected person, they can reap the benefit of that protection by living long enough to pass on their genes (sickle cell and all) to their children, thus propogating the presence of sickle cell disease. Populations in which sickle cell is more prominent are those in whom the disease confers some protection (ie: populations in africa, south East Asia, etc... where malaria is rampant, health care is poor, and the presence of sickle cell makes a significant difference in determining whether one survives in the presence of malaria or not).

Answer 3

People can only get sickle-cell disease if their ancestors came from regions in Africa where the inhabitants carry sickle-cell genes.

Sickle-cell disease is an inherited condition that originally occurred in African regions where malaria is present. A person who inherits a single sickle-cell gene has a tolerance for malaria and will have fewer symptoms if they become infected with malaria. Therefore, in those regions, sickle-cell genes were beneficial and became widespread.

Unfortunately, anyone who inherits two sickle-cell genes will have sickle-cell disease.

Answer 4

Because Sickle cells were originally in Africa to fight off malaria (A disease caused by a mosquito bite).