Primase synthesizes short stretches of RNA nucleotides providing a 3OH group to which DNA polymerase can add DNA nucleotides

ated with replication; the other three have specialized functions in DNA repair (Table 12.3).

DNA polymerase III is a large multiprotein complex that acts as the main workhorse of replication. DNA poly-merase III synthesizes nucleotide strands by adding new nucleotides to the 3' end of growing DNA molecules. This enzyme has two enzymatic activities (Table 12.3). Its 5':3'

polymerase activity allows it to add new nucleotides in the 5' : 3' direction. Its 3' : 5' exonuclease activity allows it to remove nucleotides in the 3' : 5' direction, enabling it to correct errors. If a nucleotide having an incorrect base is inserted into the growing DNA molecule, DNA polymerase III uses its 3' : 5' exonuclease activity to back up and remove the incorrect nucleotide. It then resumes its 5' :3'

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