single nucleotide polymorphisms


sin·gle nu·cle·o·tide pol·y·mor·phisms

(sing'gĕl nū'klē-ō-tīd pol'ē-mōrph'izmz) Variation between two DNA sequences consisting in the difference of a single nucleotide, frequently the substitution of thymine for cytosine. Although the possession of a pair of alleles displaying such polymorphism seldom causes demonstrable abnormality or malfunction, it may influence the response to pathogens, toxins, and environmental agents and enhance susceptibility to certain conditions.