Question

1. What are the functions of the following enzymes in E. coli?
   1. DNA polymerase I __________________________________________________
   2. DNA polymerase II __________________________________________________
   3. DNA polymerase III _________________________________________________
   4. DNA polymerase IV _________________________________________________
   5. DNA polymerase V _________________________________________________

Please indicate (if possible) which is the evolutionary history of these polymerases? Which of them you could be eliminate and preserve the function of the organism? (you must eliminate 2)  What will be the consequences? Which environment might be suitable for the survival of this “mutant” that you created?

Answer 1

Question

a. The function of DNA polymerase I

Help to repair any damage in the DNA and connect okazaki fragments present on lagging strand of DNA.

b. The function of DNA polymerase II

Help in repairing of damage DNA

c. The function of DNA polymerase III

Mainly involved in the replication of DNA in 5'->3' direction and involved too in 3'->5' exonucleotic editing of mispaired DNA.

d. The function of DNA IV

It is involved in the non-targeted mutagenesis

e. The function of DNA V

It is involved in the DNA repair mechanism in prokaryotes.

The evolutionary history of these polymerase is still unclear in case of prokaryotes. But it is thought that DNA polymerase III was the first enzyme to evolve as it perform both replication and repair mechanism. We can eliminate DNA polymerase I and DNA polymerase IV but still could have preserved the function. The consequence will be that bacteria DNA would have high risk of mutation . The environment that would be best to grow for this mutant bacteria would be the media with proper nutrient and favorable environment conditions.