CEM 311 Lecture Notes - Lecture 39: Dna Polymerase Iii Holoenzyme, Dna Replication, Proofreading
Document Summary
Mistakes during the process are extremely rare. Dna pol iii makes only one mistake per 108 bases made. Dna replication proceeds bidirectionally from many origins of replication. Why is fidelity high in dna replication: instability of mismatched pairs, configuration of the dna polymerase active site, proofreading function of dna polymerase. Complementary base pairs have much higher stability than mismatched pairs. Stability of base pairs only accounts for part of the fidelity. *error rate for mismatched base pairs is 1 per 1,000 nucleotides. Dna polymerase is unlikely to catalyze bond formation between mismatched pairs. This induced-fit phenomenon decreases the error rate to a range of 1 in 100,000 to. Dna polymerases can identify a mismatched nucleotide and remove it from the daughter strand. The enzyme uses a 3" to 5" exonuclease activity to digest the newly made strand until the mismatched nucleotide is removed. Dna synthesis then resumes in the 5" to 3" direction.
