DNA replication machinery III

Question 1

Accuracy of DNA replication

Answer 1

• dependent on correct hydrogen bonding between incoming nucleotides and template
• must be extremely accurate
• DNA pol is a template-directed enzyme

Question 2

Proofreading activity of DNA Pol

Answer 2

• produced by change in the location of hydrogen atoms on bases
• spontaneous mutations can result from mispairing to tautomers during DNA replication
• DNA Pol have proofreading activity to avoid this

Question 3

Describe the mechanism of DNA Pol proofreading activity

Answer 3

• nucleotide enters site on DNA pol and forms bond
• DNA pol advances one nucleotide
• in case of mismatch, enzyme retreats 1nt and DNA polymerase activity ceases
• latent 3’-5’ exonuclease is activated