Sickle Cell Anemia - Research Paper Example

Sickle Cell Anemia Single cell anemia is a hereditary disease that often characterized with abnormal red blood cells assuming rigid sickle shapes instead of the normal biconcave shape. The condition normally results in severe symptoms including anemia, pain and various life threatening complications associated with decreased flexibility of red blood cells. Sickle anemia is particularly caused by the mutation of a gene that is responsible for making hemoglobin proteins that carry oxygen in the red blood cells. Individuals with one copy of the mutant (sickle cell) gene normally display both abnormal and normal hemoglobin but do have the disease. On the other hand, individuals with two copies of the mutant version of the hemoglobin gene are likely to develop full blown sickle cell anemia (Malowany 49). According to the Darwinian theory of evolution, the existence of sickle cell anemia in only certain geographical regions of the world particularly those prone to malaria is a good example of an evolutionary trade off during the process of natural selection. In his book, the Origin of the species by natural selection, Darwin particularly outlined the steps of survival for the fittest by arguing that populations often show variations in virtually all traits and that certain variations can improve the survivorship of individuals or organisms(improving their fitness). On the other hand, the theory also suggests that the frequency of these variations may increase with each generation if they are heritable. The evolutionary trade off between Sickle cell anemia and Malaria was first highlighted after the discovery that the geographical distribution for the sickle cell allele known as hemoglobin S was virtually overlapping with the geographical distribution of Malaria (Hiren 25). This is particularly based on the notion that sickle cell heterozygote are often resistant to malaria and therefore individuals with sickle cell traits have a survival advantage in Malaria prone regions such as West Africa as compared with individuals with normal hemoglobin. Malaria is a common tropical disease caused by a protozoan P. falciparum which is largely transmitted through mosquito bites. The protozoa then infect the red blood cells of the victim and multiply thereby becoming available for transfer to other susceptible individuals via mosquito bites. According to Tapper (134), malaria is a disease that has existed in Africa and other tropical regions for several millennia. Overtime, the persistence presence of Malaria particularly in central and Western Africa began to form a selective pressure, thereby not only influencing the genetic development individuals resistant to the disease but also enhancing their survivability. On the other hand, Sickle cell is known to affect the hemoglobin and hemoglobin molecules referred to as hemoglobin S (Hgb. AS) are typical among fellows with this specific hemoglobinopathy. Consequently, the protection against malaria seen in carriers of sickle cell anemia is considered to be a form of genetic trade off. A number of researchers have asserted that Hgb. AS mutation which provides a certain level of prevention against malaria never developed as straight response towards the malaria parasite. Instead, it developed by chance. Individuals without the mutation residing in places that are endemic for malaria remained at a higher risk of contracting the malaria parasite followed by the development of this given infectious disease. Symptoms like enlarged spleens and high fevers were common among the affected individuals. Besides, it was observed that carriers of HGB. AS had higher chances of survival whenever malaria struck in comparison with the Hgb. AA carriers who always died during their first year of life if infected with malaria. Although the exact mechanism of how Sickle cell allele(S) impairs the development of Malaria is not yet fully known, it is widely believed that the infection of sickle cell trait red blood cells by P. falciparum often deform them in a way that they are marked as abnormal by macrophages before they are subsequently removed from the circulation and destroyed in the spleen together with the parasite (Ferreira 342). Other studies have suggested that the conditions in sickle cell trait erythrocytes may directly kill the Malaria parasites thereby impairing their proliferation. For example, some ultrastructural studies have revealed that incubating P. falciparum parasites at low oxygen tension similar to that of the sickle trait erythrocytes may cause extensive metabolic damage to the parasites. Lastly, it has also been suggested that sickle trait red blood cells often produces higher levels oxygen radical formations that are toxic to a diverse number of pathogens including the malarial parasites. Generally, despite the existence of contradicting speculations regarding the relationship between Sickle cell anemia and Malaria, scientists concur that that the abnormal hemoglobin found in people with sickle cell traits is particularly less hospital to Malaria parasites(P. falciparum), thereby providing a form of protection against malaria to individuals with the genetic trait (Ferreira 346). With malaria being a serious disease affecting nearly 500 million people ad claiming the lives of nearly 2 million people in the world every year, resistance to malaria can provide a significant selective potential to the sickle cell allele(S) heterozygote individuals. The theory regarding the evolutionary trade off between sickle cell and malaria is perhaps one of the most widely used evolutionary reasoning used to understand an epidemiology of a disease. It is worth noting that it is the only carrier state of the sickle cell anemia that may confer benefits to individual living in Malaria endemic areas as the homozygous sickle cell anemia if normally fatal, and it is unlikely that such persons may reach the reproduction age to be able to pass their genes to the next generation (Malowany 52). This also means that sickle cell anemia also acts as a negative selective mechanism. For example, throughout the history of Africa and other malaria prone regions, people without sickle-cell genes have always died from malaria, mostly before their reproductive age. Consequently many people in such regions ended up being carriers for the sickle cell trait, which gave them a genetic advantage since carriers are conferred a protection against malaria while at the same time they are asymptomatic for sickle-cell anemia. This explains why many people in the high risk malaria regions of the world are sickle cell trait carriers (heterozygotes). However, although sickle cell trait carriers are less likely to develop Malaria, they are capable of transmitting a defective gene to their offspring. The phenomenon is one of the best evidence that natural selection plays a critical role in the maintenance of certain genetic states. For example, carriers of sickle cell traits are likely to survive and pass their genes to the next generations. Nevertheless it is worth noting that this is a deflect and not an increased complexity which is used as a selective mechanism and having many carriers in these regions only means that more people are likely to suffer from the terrible disease of sickle cell anemia. In the contemporary post-Darwinian era, the growing knowledge in the evolutionary trade off that occurs in diseases and pathogens is increasingly applied as a basis of emerging medical treatments including the current antiretroviral treatment of HIV patients (Luzzatto 51).The evolutionary trade off between sickle cell anemia and malaria serves one of the best examples of how knowledge about evolution can effectively be used to influence the practice of medicine. Behind the question on whether sickle-cell concept has helped in establishing Darwinian evolution lies an assumption that observing an adaption that entails mutation in some way has the implication that a number of the more complicated forms witnessed today have their basis in the simple forms traced back to single-cell organisms. Whereas natural selection is a fact, people’s attention towards selection hypothesis is often overdone while ignoring other factors. In a single instance, it was revealed that out of ten West Africans residing within the UK and carrying the sickle-cell trait, five had genetic predisposition to stuttering (Thompson 63). The temptation of using natural selection based explanations in establishing a linkage between stuttering gene frequency and childhood malaria and sickling did overlook certain important sociological facts. Additionally, it has also inspired many evolutionary scientists to investigate the potential evolution of other possible genetic disease protection mechanisms suspected of having some genetic trade offs such as the correlation between inheritance of the gene for cystic fibrosis and increased susceptibility to tuberculosis. Lastly, numerous arguments such as those suggesting that depression may be serving evolutionary purposes have also been made and research in this exciting field is still on going. Just like evolutionary theory has profoundly impacted on our lives, the emerging Darwinian medicine is poised to significantly alter our understanding of diseases and pathogens (Malowany 54). However, the impact of evolution on the biochemical and molecular facts of human medicine are often quite complex. In conclusion, the evolutionary trade off between Sickle cell anemia and Malaria is particularly evidenced by the virtually overlapping the geographical distribution for the sickle cell allele known as hemoglobin S was virtually with the geographical distribution of Malaria. Despite the fact that the exact mechanism of how Sickle cell allele(S) impairs the development of Malaria is not yet fully understood, it is widely believed that the abnormal hemoglobin found in people with sickle cell traits is significantly less hospital to Malaria parasites (P. falciparum), thereby providing a form of protection against malaria to individuals with the genetic trait. Works Cited Ferreira A, Marguti I. Sickle hemoglobin confers tolerance to Plasmodium infection. Cell 145.2 (2011):398-409. Print. Hiren, Dhanani. “Sickle Cell Disease: History and Origin.” The Internet Journal of Haematology 1.2(2004): 23-28. Print. Luzzatto, Lucio. Sickle Cell Anaemia and Malaria. Mediterr J Hematol Infect Dis. 4.1. (2012): 43-54. Print. Malowany, Butany J. “Pathology of Sickle Cell Disease.” Diagnostic Pathology 29.1(2012):49-55. Tapper, Melbourne. In The Blood: Sickle Cell Anemia and the Politics of Race. University of Pennsylvania Press, 2009.Print. Thompson, Paul. The Structure of Biological Theories. New York: State University of New York Press, 1989. Print. Read More