<P> The term proofreading is used in genetics to refer to the error - correcting processes, first proposed by John Hopfield and Jacques Ninio, involved in DNA replication, immune system specificity, enzyme - substrate recognition among many other processes that require enhanced specificity . The proofreading mechanisms of Hopfield and Ninio are non-equilibrium active processes that consume ATP to enhance specificity of various biochemical reactions . </P> <P> In bacteria, all three DNA polymerases (I, II and III) have the ability to proofread, using 3' → 5' exonuclease activity . When an incorrect base pair is recognized, DNA polymerase reverses its direction by one base pair of DNA and excises the mismatched base . Following base excision, the polymerase can re-insert the correct base and replication can continue . </P> <P> In eukaryotes only the polymerases that deal with the elongation (delta and epsilon) have proofreading ability (3' → 5' exonuclease activity). </P>

Why proof-reading is an essential function for dna polymerase iii
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