Single-nucleotide polymorphisms (SNPs, pronounced “snips”) are the most common type of genetic variation among people. Each Single-nucleotide polymorphisms represents a difference in a single nucleotide. For example, a single-nucleotide polymorphisms may replace the cytosine (C) with the thymine (T) in a certain strech of DNA. SNPs occur normally throughout a person’s DNA and these variations are usually harmless and do not affect health or development. However, some SNPs are associated with health conditions or disease predisposition, and others may influence how an individual responds to certain drugs. SNPs are also valuable in biomedical research and genetic testing because they can act as biological markers, helping scientists locate disease-associated genes.