ABSTRACT
E. coli DNA polymerase I requires several deoxynucleoside 5'-triphosphates (dNTPs) as precursors, Mg2+, a DNA template and a primer with a 3'-OH end. DNA polymerase I also corrects mistakes in DNA by removing mismatched nucleotides. DNA synthesis then proceeds outward in both directions from the single origin. The products of the reaction are two daughter double-stranded DNA molecules each of which has one original template strand and one strand of newly synthesized DNA. DNA polymerase cannot start DNA synthesis without a primer. Even on the lagging stand, each Okazaki fragment requires an RNA primer before DNA synthesis can start. DNA polymerases I and III, primase and DNA ligase are not the only proteins needed for replication of the bacterial chromosome. The DNA template is a double helix with each strand wound tightly around the other and hence the two strands must be unwound during replication.
