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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 andhomozygote recessives are strongly resistant. The

most common genotype for the HIV resistance gene

is homozygous dominant with two copies of the

DNA code

GTCAGTATCAATTCTGGAAGAATTTCCAGACA. Thegenotype 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

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typically have lesser rates of HIV infection than

patients with the common allele of two copies of

the DNA code. Yet this doesnt necessarily meanthey prevent complete infection for the long term,

but rather simply slowing down the process for

heterozygotes. Homozygous are completely

immune to the infection.

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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.

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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.

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Pro/Con of rs333 SNP Awareness

There are a number of reasons why one wouldwant 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 inactivities 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

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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.