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SNP Basic Background information

We worked with the SNP rs333, which contains 32 nucleotides. The allele is positioned on chromosome number 3 of the CCR5 gene and the SNP is a frame shift mutation. The genotype for HIV resistance for SNP rs333 is homozygous recessive. Heterozygotes are partially resistant and homozygote recessives are strongly resistant. The most common genotype for the HIV resistance gene is homozygous dominant with two copies of the DNA code GTCAGTATCAATTCTGGAAGAATTTCCAGACA. The genotype that contributes to the partial resistance of HIV is one copy of the DNA code GTCAGTATCAATTCTGGAAGAATTTCCAGACA. Maximum resistance is present in human beings with no copies of the DNA code. This SNP slows down the progression of the HIV infection disease. People that are heterozygous

typically have lesser rates of HIV infection than patients with the common allele of two copies of the DNA code. Yet this doesnt necessarily mean they prevent complete infection for the long term, but rather simply slowing down the process for heterozygotes. Homozygous are completely immune to the infection.

How does it prevent HIV?

During a typical HIV contraction, the CCR5 receptor acts as a target cell for infection. Located on the helper T cells of CCR5 genes are specific protein receptors called a chemokine receptors. The HIV virus specifically binds to the external proteins of the helper T cells, allowing HIV to enter it via endocytosis. Because of this, HIV resistance is distinguished by the deletion of the 32 base pairs in the CCR5 gene. So, when a person is missing the 32 base pair sequences, their helper T cells are absent of the chemokine protein receptors. As a result, the HIV virus cannot bind to and enter the helper T cells, thus the infection is prevented.

Occurrence Rate
CCR5 expression and presence is increased in patients experiencing HIV infection. So by knowing that HIV infection leads to a higher amount of CCR5 production than normal, we can measure the expression of CCR5 and use it as an indicator for ones HIV disease progression. In an experiment done by the NCBI (National Center for Biotechnology Information), individuals from many different ethnic backgrounds were tested for the rs333 mutation. Out of the 48 Africans and 46 Pacific islanders studied, none of them had the beneficial mutation that prevented HIV. Out of a group of 46 Hispanics, one person was heterozygous for the rs333 mutation, and the rest were normal. Out of 62 Caucasians, 6 were heterozygous for the mutation, which means that they have a lower chance of getting HIV, but none were homozygous recessive.

Pro/Con of rs333 SNP Awareness

There are a number of reasons why one would want to know their rs333 SNP genotype. Most importantly, this awareness could act as an important step toward prevention. One would be able to identify their risk of contracting HIV. This could aid in minimizing or avoiding participation in activities such as sexual intercourse or drugs. If someone knew of their higher susceptibility, they could choose not to have a child if their baby would have a higher risk of developing AIDS. In addition, knowledge about ones self could allow others such as researchers and biologists practice studies to further understand the rare condition. As a result, they could become closer to developing a cure for those that are also affected to benefit everyone. The rs333 SNP is present in people with resistance to a fatal disease. Because of this rare

benefit, almost everyone would want to find out if they had the rs333 SNP. Since the SNP is linked to a decreased risk of type 1 diabetes and an abnormally excessive growth of large blood vessels, genotype awareness could help influence ones diet. By knowing one was at a lower risk for diabetes, they might not fear the disease and eat a sugar high diet. At the same time, learning that ones blood vessels expand beyond normal size, they could seek medical treatment before the trait develops into a problem. For these reasons, most people would want to know if they had the rs333 SNP. One would not be worried of carrying the rs333 SNP. Unlike damaging and fatal traits such as malaria or AIDS, this trait is not a sensitive one to discuss about because it codes for a advantageous frameshift mutation that prevents a person from contracting HIV.