Why is sickle cell anemia thought to be a response to the evolutionary pressure of malaria?
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People who are heterozygous (carriers) for sickle cell anemia have resistance to malaria. Carriers can have what is called "sickle cell trait" because they may show only slight symptoms during severe exertion. Two carriers have a 25% chance of having a child with sickle cell anemia.  These children have an increased death rate, even in their twenties during child rearing years.  Since areas of Africa with the highest malarial rates show the highest sickle cell rates, the trait seems to be selected for evolutionarily.
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the specific mutation of the hemoglobin chain creates a less friendly environment for the malarial protazoans.  scientist aren't quite sure yet what it is that makes it less friendly.  but because of this people in mediteranean and african areas are who have one copy of the faulty gene are more immune to malarial infections which will give them a greater chance to survive long enough to reproduce, thus increasing the prevalance of the mutated gene in the population.  natural selection, my friend.
246000
Because of evolution and adaptation.
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The "sickle cell" gene (technically, allele) is a result of a mutation that modifies the shape of red blood cells. It's what is known as an incompletely recessive trait, meaning that a person with one copy of the sickle cell allele and one copy of the normal allele has mostly normal red blood cells with a few sickled ones. This state has been shown to give the person carrying it resistance to malaria, a common and often fatal disease in tropical regions, particularly Africa. \nThus in Africa, the sickle-cell allele would have been rendered more common by natural selection, since being resistant to malaria was a huge advantage. The children of two people carrying the sickle-cell trait have a 25% chance of receiving both sickle-cell genes from their parents, which is known as sickle-cell anemia. \nIt's not that only people of African descent can have sickle-cell anemia, but through selection the responsible gene was made more common because of malaria resistance. The same would not be the case in areas of the world where malaria was not common; which is why people whose ancestors came from other places are not as likely to have two parents carrying the sickle-cell trait.
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There is no specific treatment for sickle cell anemia. People with this disease should avoid high altitudes, maintain adequate fluid intake, and treat infections promptly. \nA bone marrow transplant is the only available treatment that can cure the disease, however, its use remains uncommon. \nDuring a sickle crisis, certain therapies may be necessary. Painful episodes are treated with analgesics and adequate liquid intake. Treatment of pain is critical. Non-narcotic medications may be effective, but some patients will require narcotics. \nHydroxyurea (Hydrea) was found to help some patients by reducing the frequency of painful crises and episodes of acute chest syndrome and decreasing the need for blood transfusions. There has been some concern about the possibility of this drug causing leukemia, but as yet there are no definitive data that Hydrea causes leukemia in sickle cell patients. \nThe main thing is to try to avoid sickle cell crisis, which include steps to reduce the chance of hypoxia, such as climbing high altitudes, and seeking medical attention quickly to counteract problems such as upper respiratory tract infections.
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The spleen is the site for lymphocytes proliferation and immune surveillance. It is also responsible for blood cleansing. It extracts aging blood cells and platelets from the blood. It also stores some of the breakdown products of blood, like iron, for reuse. \n    I would think that since malaria is a parasite that enters the red blood cells, this is how it affects the spleen. It probably causes the spleen to clean out the infected cells which will cause the blood to have too few red blood cells, maybe causing something like anemia? this last part is only a guess though.
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I wasn't satisfied with any of the above answers, so I thought I'd write my own:\n  For evolution to take place, people would have to die because of a certain trait..... for example, if more short people died in a certain generation, then the next generation would be slightly taller because there were less short people.  That's why people won't ever have 6 fingers... because why would people be able to survive better with 6 fingers than 5?  To evolve, you need death of a certain population.  \n  Humans have been able to control their environment and have used medicines to cure many diseases.  An interesting case of a type of evolution would be people in Africa with Sickled Cell Anemia (where red blood cells change shape into a half moon instead of round).  People that have one Sickled Cell allele, and one normal cell allele will have some normal red blood cells and some sickled.  Malaria can only attack normal red blood cells and so these people with both survived through Malaria.  Therefore, there will be more sickled cell alleles in that community because the people without them died.  That is why there are more cases of sickled cell anemia in african people.
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there is no cure for sickle cell anemia
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Here's more info mrom Wiki for you:\nSymptoms of malaria include fever, shivering, arthralgia (joint pain), vomiting, anaemia caused by haemolysis, haemoglobinuria, and convulsions. There may be the feeling of tingling in the skin, particularly with malaria caused by P. falciparum. Consequences of infection with malaria include coma and death if untreated—young children and pregnant women are especially vulnerable. Splenomegaly (enlarged spleen), severe headache, cerebral ischemia and hemoglobinuria with renal failure may occur.\n[edit]\n\nMosquitoes\n\nOnly females feed on blood, thus males do not transmit the disease. The Anopheles species prefer to feed at night. They usually start searching for a meal at dusk, and will continue throughout the night until taking a meal. Young mosquitoes first ingest the malaria parasite by feeding on a human carrier. Infected female Anopheles mosquitoes carry Plasmodium sporozoites in their salivary glands.\n[edit]\n\nThe malarial parasite\n\nWhen an infected mosquito pierces a person's skin to take a blood meal, the sporozoites in the mosquito's saliva enter the bloodstream and migrate to the liver. There they hide within liver cells and multiply asexually for a period of 6 to 15 days. Within the liver cells the parasite differentiates to produce hundreds or thousands of merozoites which, following rupture of the cell, are released into the blood stream and invade red blood cells.\n\nIf a mosquito pierces the skin of an infected person, it potentially picks up gametocytes with the blood, fertilization occurs in the mosquito's gut which means the mosquito is the definitive host of the disease. New sporozoites develop and travel to the mosquito's salivary gland, completing the cycle. Pregnant women are especially attractive to the mosquitoes, and malaria in pregnant women is an important cause of stillbirths, infant mortality and low birth weight.
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What a fascinating question.  I'm no geneticist, so take my words with such forewarning.\n\nI think if one were to closely look at human evolution, one would find a different degree in evolutionary history.  \n\nHow does one best differentiate the degree between races? That is not so debatable. Most scientist, today, do not recognize race.\n\nOnce upon a time they did it with "discernible" qualities based on "eyeball" measurements.  \n\nSkin color demonstrates this old fashioned method quite well.  And still, it counts for something, despite its inaccuracy.  \n\nOur world wide communication has increased, and people of different skin colors have discussed (and seem to agree) that human nature seems to be same, no matter where we are.  \n\nThere are good and bad people out there, despite the preponderance of race you live amongst.  \n\nThis could be comforting in the sense that no race is better than the other,  or discomforting in the sense that there will always be "different" people out there, no matter where you live.\n\nThe debate on "degree" of human evolution, in my humble opinion, should be viewed in light of the environment in which the human is required to adapt to.\n\nYes the degree of evolution among Humans is different, and so is the environment in which Humans live in.\n\nA current trend for scientist is to observe closely the Human genome and how it may or may not change within different situations.\n\nI suppose the phrase of "genetic adaptation" is appropriate to use here.\n\nSpecifically, I'm thinking of the adaptation of the Human gene 'hemoglobin' has gone through, in an attempt allow Humans to survive.  \n\nIn some environments Plasmodium parasitism has changed the degree of evolution by favoring the level of genetic adaptation in those with an altered (or evolved?) globin genes.  Having those altered genes in an an environment where Plasmodium is prevalent is a plus. (Please google "genes, hemoglobin, parasites, Africa).\n\nHaving those altered globin genes in a part of the world where Plasmodium is NOT prevalent might mark you as different.  Just like skin color.\n\nI sometimes wonder if race might better be described by historic ability to survive genetic insults.  \n\nDo you have an Alu element in NM_94327343?\n\nOr better yet, are you evolving differently because your Alu element at NM_94327343 is no longer methylated?\n\nTake home points: (1) Skin color is not a current basis of race.  (2) Environment suggestively role-plays in our differences during Human evolution.  (3) According to experts every time the sperm and egg "dance", there is an opportunity for a degree for evolution (Sorry I didn't expound on this in my answer, but it can be googled.  Try 'XX', 'XY', 'meiosis' as a point in a good direction).  (4) There are probably other reasons that Humans evolve to different degrees, and they might be unmeasurable at the moment. However, current standard genetic measures on "old" populations seems to say "yes, there are degrees of difference in human evolution".  \n\nI had a lot of fun thinking about your question.  I can't wait to see your other replies regarding this topic.  Don't forget to pass on your good Karma!
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wow, that's all so wrong in so many ways.  staphylococcus is a genus of bacteria.  not a virus at all. and speaking of not a virus at all, malaria isn't caused by viruses or bacteria, but by parasites.\n\nany doctor who said that is...wow... really, really awful.
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not only do the insects not live there, North Eastern people are subject to sickle cell virus, which helps protect against malaria type diseases. Sickle cell genes are heterozygous advantage
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My boyfriend has sickle cell anemia and I'm learning how to deal with it and learn about especially considering we don't have medicare for him to get prescriptions.  From what I've read, the anemia does not affect your diet but your diet can affect the anemia or at least its symptoms.  For example, those with sickle cell anemia have a reduction in oxygen at times and therefore, it is very important to always drink plenty like 10 or more glasses of water a day.  Also, fruits and vegetable are often aids in oxidation and help to keep the body healthy.  Exercise, not smoking or drinking alcohol, and staying away from agitates like dust are also important.
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SYMPTOMS include fever, shivering, arthralgia (joint pain), vomiting, anemia due to hemolysis, hemoglobinuria, and convulsions. There may be the feeling of tingling in the skin, particularly with malaria caused by P. falciparum. Complications of malaria include coma and death if untreated—young children and pregnant women are especially vulnerable. Splenomegaly (enlarged spleen), intense headaches, cerebral ischemia and hemoglobinuria with renal failure may occur.\n\nCAUSED BY Infected female Anopheles mosquitoes carrying Plasmodium sporozoites in their salivary glands. Once an infected mosquito pierces a person's skin to take a blood meal, which they usually do starting at dusk and continuing throughout the night, the sporozoites enter the person's body via the mosquito's saliva, migrate to the liver where they multiply within hepatic liver cells asexually. Development in the hepatic cell takes 6 to 15 days depending on the species. Within hepatic cells the parasite replicates to produce hundreds or thousands of merozoites which, following rupture of the hepatic cell, are released into the blood stream and invade red blood cells.\n\nTREATMENT There are several families of drugs used to treat malaria. Chloroquine was the antimalarial drug of choice for many years in most parts of the world. However, resistance of Plasmodium falciparum to chloroquine has spread recently from Asia to Africa, making the drug ineffective against the most dangerous Plasmodium strain in many affected regions of the world.\n\nThere are several other substances which are used for treatment and, partially, for prevention (prophylaxis). Many drugs can be used for both purposes; larger doses are used to treat cases of malaria. Their deployment depends mainly on the frequency of resistant parasites in the area where the drug is used.\n\nIt is common in people from parts of the world where malaria is or was common, especially in West Africa or in descendents of those peoples. Sickle cell disease can occur in any individual of any color or ethnicity, however
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My father had malaria when he was living in Africa. And as far as I know he has malaria once in a while, even though it is 30 years later.\nThis disease is transmitted to humans by a mosquito bite. He has bronchitis once in a while, and it is in these periods that the malaria manifests, because body defences are low and susceptible to diseases. Now he knows how to treat it, but sometimes it is quite severe: headaches, severe temperature, chills, vomiting, etc.\nYou can prevent malaria by taking for example quinine doses everyday, but it cannot guarantee that you won't catch it, another way to avoid it, is to use insect nets, and stay away from mosquito areas at dusk and night. Because that's the time of the day, that mosquitoes look for human blood as it has proteins essential for their reproduction system (most people think they feed on our blood, but that is not true. Only female mosquitoes bite and it is a reproduction thing. If they fed on our blood male mosquitoes would bite as well)\nThis disease will never go away. When the mosquito bites, its saliva goes straight to the liver. Time from time parasites will be release in the blood stream and infect the body with malaria. \n\nI hope I helped. At least I wrote almost everything I know about malaria and mosquitoes.
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You can write on Sickle Cell Anemia...
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I asked this question recently myself. I have faith that they are out there, and we will see them someday. Some of the blood of these tribes probably got mixed with regular people. There is some evidence of this with Africans, particularly Ethiopia.