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How does DNA polymerase use the structure of DNA to catch errors? DNA polymerase moves along a single strand of DNA, building the complementary strand as it goes. The two stranded molecule passes through the DNA polymerase molecule after synthesis is complete. If the wrong base is inserted then the bond is unstable. Because the double strand is passing through the DNA polymerase the missing base can be detected and replaced. The replacement is done by a different part of the enzyme. If DNA polymerase did use single stranded DNA as a template and the completed double strand did not continue to interact with the enzyme after synthesis then the number of errors in DNA replication would be much higher.