A Mutation Story Have you ever wondered about the genetic mutation that affected the population of West Africa? Well, I always had that thought in my mind! So I thought why not write about it. So I did! The article that I chose was “A Mutation Story” from http://sepuplhs.org/. This section tells the story of a genetic mutation affecting the population of West Africa. Even though this mutation is helpful in avoiding malaria, this mutation can also lead to sickle cell anemia. Sickle cell specialist Dr. Ronald Nagel stresses the genetic variety necessary for the existence of a species. A gene known as HbS was the center of a medical detective story that began in the middle 1940s in Africa. Doctors noticed that patients who had sickle cell anemia, a serious inherited blood disease, were more likely to survive malaria. What was confusing was why sickle cell anemia was so dominant in some African populations. How could the mutation that causes the deadly sickle cell disease -- also be helpful? On the other hand, if it didn't provide some survival advantage, why had the sickle gene continued in such a high occurrence in the populations that had it? The sickle cell mutation is like a typographical error in the DNA code of the gene that tells the body how to make a form of hemoglobin (Hb), the oxygen-carrying molecule in our blood. Every person has two copies of the hemoglobin gene. Usually, both genes make a normal hemoglobin protein. When someone receives two mutant copies of the hemoglobin gene, the abnormal form of the hemoglobin protein causes the red blood cells to lose oxygen and twist into a sickle shape during periods of high activity. These sickled cells become stuck in small blood vessels, causing a "crisis" of pain, fever, swelling, and tissue damage that can lead to death. This is sickle cell anemia. But it takes two copies of the mutant gene, one from each parent, to give someone the full disease. Many people have just one copy, the other being normal. Those who carry the sickle cell trait do not suffer nearly as severely from the disease. Researchers found that the sickle cell gene is especially predominant in areas of Africa hard-hit by malaria. In some regions, as much as 40 percent of the population carries at least one HbS gene. It turns out that, in these areas, HbS carriers have been naturally selected, because the trait discusses some opposition to malaria. Their red blood cells, containing some abnormal hemoglobin, tend to sickle when they are infected by the malaria parasite. Those infected cells flow through the spleen, which get rid of them out because of their sickle shape -- and the parasite is eliminated along with them. Scientists believe the sickle cell gene appeared and disappeared in the population several times, but became permanently recognized after a particularly venomous form of malaria jumped from animals to humans in Asia, the Middle East, and Africa. In areas where the sickle cell gene is common, the protection discussed has become a careful advantage. Unfortunately, it is also a disadvantage because the chances of being born with sickle cell anemia are relatively high. For parents who each carry the sickle cell trait, the chance that their child will also have the trait -- and be immune to malaria -- is 50 percent. There is a 25 percent chance that the child will have neither sickle cell anemia nor the trait which enables protection to malaria. Finally, the chances are that their child will have two copies of the gene, and therefore sickle cell anemia, is also 25 percent. In conclusion, a gene known as HbS helps prevent malaria as well as lead to sickle cell anemia. What was confusing was why sickle cell anemia was so dominant in some African populations. Researchers found that the sickle cell gene is especially predominant in areas of Africa hard-hit by malaria. 40 percent of the population carries at least one HbS gene in this region. It turns out that, in these areas, HbS carriers have been naturally selected, because the trait discusses some opposition to malaria. One topic that was discussed in this article that I would like to explore more about is hemoglobin. Well, the thought about the genetic mutation in West Africa has cleared out of my mind!
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