Single Nucleotide Polymorphisms, popularly called SNPs are a kind of genetic variation commonly seen in people. Each SNP stands for a variation in a single nucleotide. The structure of SNPs variants differs from the original nucleotide as one nitrogen base in a nucleotide is replaced by another. For example, the nitrogen base cytosine may get replaced with thymine in an SNP along a particular stretch of DNA.  .

SNPs can occur anywhere in a person’s DNA. There is almost one SNP every 1,000 nucleotides on an average. This means that there are at least 4-5 million SNPs found in a person’s genome. There are about 600 million SNPs known in populations across the world.

Most  SNPs do not affect a person’s health or development. However, some SNPs play an important role in determining a person’s response to certain drugs, risk of developing a disease, or the individual’s predisposition to environmental factors, like toxins, allergens.