Single nucleotide polymorphisms

SNPs (pronounced “snips”) are the most common type of genetic variation among people. Each SNP represents a difference in a single DNA nucleotide. SNPs occur normally throughout a person’s DNA. They occur almost once in every 1,000 nucleotides on average, which means there are roughly 4 to 5 million SNPs in a person’s genome. These variations may be unique or occur in many individuals; scientists have found more than 100 million SNPs in populations around the world. Most commonly, these variations are found in the DNA between genes. They can act as biological markers, helping scientists locate genes that are associated with a disease.

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