DNA polymerase I (Pol I) in E. coli has three domains that each have unique func
ID: 92386 • Letter: D
Question
DNA polymerase I (Pol I) in E. coli has three domains that each have unique functions: Domain 1: Responsible for removing RNA primers during DNA replication: recall that RNaseH also serves this function. Domain 2: Serves to proofread replicated DNA to ensure fidelity during DNA replication. Domain 3: Polymerizes DNA where RNA primers have been removed. Predict the effect(s) of the following mutations on DNA replication: a) Mutation in RNaseH (no expression of the gene at all) plus a second mutation in Pol 1 so that Pol 1 is expressed but the mutant protein lacks the function of domain 1.Explanation / Answer
DNA Polymerase I (Pol I) was the first enzyme discovered with polymerase activity. Although this was the first enzyme to be discovered that had the required polymerase activities, it is not the primary enzyme involved with bacterial DNA replication. The primary enzyme involved in DNA replication is DNA Polymerase III (Pol III).
If there is a mutation in RNaseH and a second mutation in Pol I, RNA primers are not removed. The domain 2 which performs proof reading activity will detect the presence of mismatched nitogenous bases in DNA strand and the DNA replication process stops. If it continues, it decreases the efficiency and accuracy of plus strand DNA.
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