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The pairing of complementary bases in DNA (through [https://en.wikipedia.org/wiki/Hydrogen_bonding hydrogen bonding]) means that the information contained within each strand is redundant. Phosphodiester (intra-strand) bonds are stronger than hydrogen (inter-strand) bonds. The actual job of the phosphodiester bonds is where in DNA polymers connect the 5' carbon atom of one nucleotide to the 3' carbon atom of another nucleotide, while the hydrogen bonds stabilize DNA double helices across the helix axis but not in the direction of the axis.<sup id="cite_ref-19">[https://en.wikipedia.org/wiki/DNA_replication#cite_note-19 [19]]</sup> This makes it possible to separate the strands from one another. The nucleotides on a single strand can therefore be used to reconstruct nucleotides on a newly synthesized partner strand.<sup id="cite_ref-20">[https://en.wikipedia.org/wiki/DNA_replication#cite_note-20 [20]]</sup><br/>
==== <sup id="cite_ref-20">DNA polymerase</sup> ====
In general, DNA polymerases are highly accurate, with an intrinsic error rate of less than one mistake for every 10<sup>7</sup> nucleotides added.<sup id="cite_ref-pmid18166979_24-0">[https://en.wikipedia.org/wiki/DNA_replication#cite_note-pmid18166979-24 [23]]</sup> Some DNA polymerases can also delete nucleotides from the end of a developing strand in order to fix mismatched bases. This is known as proofreading. Finally, post-replication mismatch repair mechanisms monitor the DNA for errors, being capable of distinguishing mismatches in the newly synthesized DNA Strand from the original strand sequence. Together, these three discrimination steps enable replication fidelity of less than one mistake for every 10<sup>9</sup> nucleotides added.<sup id="cite_ref-pmid18166979_24-1">[https://en.wikipedia.org/wiki/DNA_replication#cite_note-pmid18166979-24 [23]]</sup>
The rate of DNA replication in a living cell was first measured as the rate of phage T4 DNA elongation in phage-infected ''E. coli''.<sup id="cite_ref-25">[https://en.wikipedia.org/wiki/DNA_replication#cite_note-25 [24]]</sup> During the period of exponential DNA increase at 37 °C, the rate was 749 nucleotides per second. The mutation rate per base pair per replication during phage T4 DNA synthesis is 1.7 per 10<sup>8</sup>.<sup id="cite_ref-26">[https://en.wikipedia.org/wiki/DNA_replication#cite_note-26 [25]]</sup><br/> <br/>
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