What are polymorphisms (SNPs)?

      There are four different types of nitrogen bases in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T). The DNA sequence that holds the information to make a protein is called a gene.

 A single nucleotide polymorphism, or SNP, is a genetic variation in a single nucleotide that occurs at a specific position in the genome where each variation is present to some appreciable degree within a population (>1%).