question_answer 45)

  The enzyme DNA polymerase in E.coli is a DNA dependent polymerase and also has the ability to proofread the DNA strand being synthesized Explain. Discuss the dual polymerase.

Answer:

                  In bacteria, three types of DNA polymerases are there. All of them can add nucleotides in5' 3' direction. They process exonuclease activity as well. DNA polymerase III can proof read the newly synthesized strand and senses the wrong base insertions. It deletes wrong bases and helps correct the mistake by putting in the right one, DNApolymerase. The only mistake it cannot corrects substitution of uracil in place of thymin. It can repair any damages done to DNA by UV exposure, etc., or the left over proofreading mistakes. It detects mutation caused by UV, removes mismatched pairs and puts back the right ones.