Snp

A single-nucleotide polymorphism (SNP) is a substitution of a single nucleotide that occurs at a specific position in the genome (DNA). Certain SNPs are associated with diseases and other traits.
The change of a nucleotide may fall within coding sequences of genes, non-coding regions of genes, or in the intergenic regions (regions between genes). SNPs within a coding sequence do not necessarily change the amino acid sequence of the protein that is produced, due to degeneracy of the genetic code.