Single nucleotide polymorphisms - Definition

A Single Nucleotide Polymorphism or SNP (pronounced snip) is a DNA sequence variation, occurring when a single nucleotide: adenine (A), thymine (T), cytosine (C) or guanine (G) - in the genome is altered. A variation must occur in at least 1% of the population to be considered an SNP.

SNPs make up 90% of all human genetic variations, and occur every 100 to 300 bases along the human genome. Two of every three SNPs substitute Cytosine (C) with Thymine (T). Variations in the DNA sequences of humans can affect how humans handle diseases, bacteria, viruses, chemicals, drugs, etc.

SNPs are of great value to biomedical research and developing pharmacy products. Because SNPs do not change much from generation to generation, it makes it easier to follow them during population studies.

References

• http://www.ornl.gov/sci/techresources/Human_Genome/faq/snps.shtml

External links

• The SNP Consortium LTD (http://snp.cshl.org/) (ability to search for SNPs)

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