What follows is from the National Center for Biotechnology Information. I think it’s one of the best descriptions of a SNP. It’s important to remember that when considering SNPs in the context of pharmacogenetics, the actual SNP may not be the cause of a particular response (as, for example, the SNP associated with the ultrametabolizer form of cytochrome P450 (CYP2D6). Some SNPs probably are causes, while others are best considered markers.

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A Single Nucleotide Polymorphism, or SNP (pronounced “snip”), is a small genetic change, or variation, that can occur within a person’s DNA sequence. The genetic code is specified by the four nucleotide “letters” A (adenine), C (cytosine), T (thymine), and G (guanine). SNP variation occurs when a single nucleotide, such as an A, replaces one of the other three nucleotide letters—C, G, or T.

An example of a SNP is the alteration of the DNA segment AAGGTTA to ATGGTTA, where the second “A” in the first snippet is replaced with a “T”. On average, SNPs occur in the human population more than 1 percent of the time. Because only about 3 to 5 percent of a person’s DNA sequence codes for the production of proteins, most SNPs are found outside of “coding sequences”. SNPs found within a coding sequence are of particular interest to researchers because they are more likely to alter the biological function of a protein. Because of the recent advances in technology, coupled with the unique ability of these genetic variations to facilitate gene identification, there has been a recent flurry of SNP discovery and detection.

Technorati Tags: pharmacogenetics, DNA, SNP

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