single nucleotide polymorphism (SNP) → πολυμορφισμός ενός νουκλεοτιδίουA single-nucleotide polymorphism (SNP, pronounced snip) is a DNA sequence variation occurring when a single nucleotide — A, T, C or G — in the genome (or other shared sequence) differs between members of a biological species or paired chromosomes in an individual. For example, two sequenced DNA fragments from different individuals, AAGCCTA to AAGCTTA, contain a difference in a single nucleotide. In this case we say that there are two alleles: C and T. Almost all common SNPs have only two alleles. The genomic distribution of SNPs is not homogenous, SNPs usually occur in non-coding regions more frequently than in coding regions or, in general, where natural selection is acting and fixating the allele of the SNP that constitutes the most favorable genetic adaptation. Besides natural selection other factors like recombination and mutation rate can also determine SNP density. SNP density can be predicted by the presence of microsatellites as regions of thousands of nucleotides flanking microsatellites have an increased or decreased density of SNPs depending on the microsatellite sequence.
Single-nucleotide polymorphism - Wikipedia, the free encyclopediaSNP (γενετικός πολυμορφισμός ενός νουκλεοτιδίου): πολυμορφισμός που προκαλείται συνήθως από την αντικατάσταση ενός νουκλεοτιδίου σε μια συγκεκριμένη θέση στην αλληλουχία του DNA από ένα άλλο.
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