BIO130H1 Lecture Notes - Lecture 9: Pyrimidine Dimer, Dna Repair, Dna Mismatch Repair
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BIO130H1 Full Course Notes
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Bio130 lecture 9: dna replication part ii and transcription part i. Two separate mechanisms: 3" to 5" exonuclease. Accidentally, incorrect base incorporated into new strand, flipped into editing pocket of polymerase, clips base off, begins again. Polymerase has already gone by and synthesized okazaki fragments. Replication unfinished: nick hasn"t been ligated together yet. Initiated by detection of distortion in geometry of double helix generated by mismatched base pairs. Eukaryotes: protein called muts which works with protein mutl. Muts is always scanning when dna is being replicated, looking for distortions. When it finds distortion, binds to it, mutl protein scans along strands looking for nick. Nick indicates that it is newly synthesized strand (error) Mutl: endonuclease type activity, excises out all bases up to and including incorrectly misincorporated base. Another dna polymerase comes in, 3" end will be available, fills gap using correct parental strand as template. Prokaryotes: pattern of methylation happens on parental strand.
