They require 1.) an existing DNA template , which they have to use as a guide to synthesize a new DNA strand
2.)A primer, with a free 3′-hydroxyl group already base-paired to the template.This is done by the enzyme Promise.Since DNA polymerase can't synthesize new DNA strand from scratch
3.) Nucleotides(Thymine, Cytosine, Adenine, or Guanine).
4.) exonuclease domain to excise incorrect base pairing in the 3' to 5' direction (a.k.a proofreading)
