Dideoxynucleotides are chain-elongating inhibitors of DNA polymerase, used in the Sanger method for DNA sequencing. They are also known as 2',3' dideoxynucleotides, and abbreviated as ddNTPs (ddGTP, ddATP, ddTTP and ddCTP).
Dideoxynucleotides are useful in the sequencing of DNA in combination with electrophoresis. The purpose of the deoxynucleotide triphosphates (dNTPs) is to supply the “bricks.” Since the idea behind PCR is to synthesize a virtually unlimited amount of a specific stretch of double-stranded DNA, the individual DNA bases must be supplied to the polymerase enzyme.