You do a series of incubations to compare the properties of E. coli DNA polymerase I and III. After incubating DNA template prepared from bacteriophage T7 with one or the other polymerase for 20 min, you add an excess of a second template, phage T3 DNA and continue the reaction for a further 40 min. You compare the amounts of T3 synthesized to the amount of T7. Most of the DNA synthesized in the polymerase I incubations is found to be T3 DNA, but almost all of the DNA in the polymerase III incubation is T7 DNA. Explain.
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coli DNA polymerase I is present and has started synthesis on T7. When you add an excess of T3 DNA, Pol I, being less processive and more prone to dissociate, readily samples the newly provided T3 templates and begins synthesizing on them. Its 5′→3′ Show more…
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