This is an animated video on DNA sequencing by Sanger's method. Sanger sequencing method is based the use of dideoxy nucleotides in the DNA polymerizing reaction. The hydroxyl group attached at the 3' end plays a very important role in DNA polymerization reaction during DNA polymerization, There is a reaction between 3'OH group and the phosphate of the new dNTP to be added. in 1977, Frederick Sanger had a brilliant idea. if the 3'OH group of the nucleotide is absent, then there wont be addition of new nucleotides and the reaction would stop. The incorporation of dideoxy nucleotide and termination of polymerization reaction is a random process. hence the overall mixture will have several fragements that have experienced the chain termination. If the length of each fragment is known then the location of nucleotides in the DNA can be estimated.