In PCR, deoxynucleotide triphosphates (dNTPs) serve as building blocks for new DNA strands. There are four different types of dNTPS, these include:
In the extension step, DNA polymerase adds free dNTPs from the reaction mixture to the template DNA in the 5’-to-3’ direction. It does so by condensing the 5’-phosphate group of a dNTP with the 3’-hydroxy group at the end of the elongating DNA strand.