single nucleotide polymorphism

(... NOO-klee-oh-TIDE PAH-lee-MOR-fih-zum) The most common type of change in DNA (molecules inside cells that carry genetic information). Single nucleotide polymorphisms occur when a single nucleotide (building block of DNA) is replaced with another. These changes may cause disease, and may affect how a person reacts to bacteria, viruses, drugs, and other substances. Also called SNP.

(Abbreviation: SNP). A genetic marker resulting from variation in sequence at a particular position within a DNA sequence. SNPs are commonly the result of transition changes (A for G, T for C), but also transversions (G or A for T or C) and single base deletions. Such variation is extensive throughout all genomes, and offers the particular advantage of being detectable without the need for gel electrophoresis.