BIO130H1 Lecture 6: Lecture 6 Part 1

• School: UTSG
• Department: Biology
• Course: BIO130H1
• Professor: Jane Mitchell

Document Summary

Dna proofreading: 3"-5" proofreading exonuclease, strand-directed mismatch repair, muts and mutl proteins, base excision repair, nucleotide excision repair. Improper nucleotide pairing prevents further elongation: cleaves improperly matched nucleotide, occurs at end of synthesized strand. Found on the e (exonucleolytic) site of dna polymerase. Polymerase: polymerizing p site and e site occur almost simultaneously. Reason of 5"-3" synthesis: allows for efficient error correction/chain growth, dna polymerase requires energy to catalyze synthesis, only 5"-3" can provide consistent energy through dntp pyrophosphate cleavage, only 5"-3" has correct orientation to cleave pyrophosphate off dntp. 3"-5" can only provide energy from the primer strand once at first dntp addition. Muts and mutl proteins: occurs after dna polymerase, but before ozaki fragment nicks have sealed, scan for geometrical distortions caused by mismatched base pairs. Proteins stop scanning when they bump into a nick on the newly synthesized strand.