Question

What would happen if we use Polymerase I instead of Polymerase III for DNA replication in a PCR? If we used an enzyme with low fidelity, how would the DNA product compare to the original template?

Answer 1

If we use DNA pol I instead of DNA pol III replication speed will be low. More time is required for DNA to replicate. This is because the low processivity of DNA pol I i.e about 40 nucleotides and it also has low polymerization rate (20 nucleotides/sec). On the other hand DNA pol III has high processivity i.e greater than 500 kb and also high polymerazation rate around 1000 nucleotides/sec). if we provide same time as for DNA pol III DNA amplification will be lesser or may not occur. One possibility is that it won't be able to amplify DNA in less time of extension period.

Fidelity tells us acurate replication of DNA. A high fidelity enzyme means it will accurately replicate DNA and make less mistakes in insertion of nucleotides. mismatches which remain are corrected by proofreading activity of enzyme. If we use low fidelity enzyme in PCR there are more mismatched nucleotides in replicated DNA as comparing with parent DNA.