Homozygous: A Genetic Analysis

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HIV first appeared in the 1980’s largely in males practicing anal receptive sexual behavior. Although HIV had not yet been characterized, medical personnel noted that this population had stubborn infections, resistant to most medications. Human immunodeficiency virus (HIV) can result in profound viremia and low T-cell counts characterized as acquired immune deficiency syndrome (AIDS). Currently, it is theorized that both strains of HIV descend from simian immunodeficiency virus (SIV) a virus that infects non- human primates. (Sharp, 2005) While other factors may have contributed to the development of genetic immunity to HIV, some studies suggest that populations which are resistant to smallpox carry the CCR5 D32 mutation. Still others consider …show more content…
It is hypothesized that this mutation enabled a select few to have immunity against smallpox. Approximately 1% of Caucasians in the US are homozygous for such a protective CCR5 variant. Similarly, the HIV infection seems follows a slower course in heterozygotes (Kumar, 2013). The CCR5 D32 mutation demonstrates its greatest prevalence at about 10% in European countries, where smallpox epidemics hit intensively between the fifth and seventh century (Galvani and Slatkin 2003). Bauduer, author of “Medical Genetic Polymorphisms as Markers of Evolutionary Forces within the Human Genome: Hypotheses Focusing on Natural Selection in the Basque Population”4 proposes a link between the smallpox outbreak and the CCR5 D32 mutation in the European population. Subsequently, the CCR5 D32 mutation and genetic immunity to HIV, has not been identified in populations that have not been exposed to smallpox (Galvani …show more content…
The smallpox virus has been existent in India as early as 1000 B.C. and had remained endemic until its final eradication in 1977. In the eighteenth century, the smallpox case fatality rate was significantly higher in Indian populations (25–50%) as compared to the populations in Europe (10%) (Saxena, 2009). Thereby, we would expect a high frequency of the CCR5 D32 mutation in populations such as India favoring the theory of selection pressure by smallpox. In fact, the frequency of the CCR5 D32 mutation exhibits low allelic frequency in this population. The presence of a low frequency of CCR5 D32 mutation, in spite of having significantly higher cases of smallpox in India than in eighteenth-century Europe, does not support the hypothesis of positive selection pressure of smallpox for CCR5 D32. (Saxena,