Biology 1001A Chapter Notes - Chapter 12.4: Dna Mismatch Repair, Exonuclease, Deoxyribonuclease
8 Apr 2018
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Mistakes made by polymerases during synthesis process. Most of the mistakes are corrected by: proofreading mechanism during replication, dna repair mechanism after replication. Proofreading mechanism depends on the polymerases" ability to back up & remove mis red nucleotides. Dna polymerase uses deoxyribonuclease to remove the incorrect nucleotide, and resumes working forward. Only correct pairs allow stable h-bonds to form. 1 mistake for every 10000 nucleotides, extremely low. 12. 4 b) dna repair corrects errors that escaped proofreading. Base-pair mismatches that were missed by proofreading mech. will be corrected by dna repair mechanism. Mismatched bases are either too large or too small, since purines and pyrimidines are supposed to t together to remain constant width in dna strand. Mismatched pairs distorts the structure of dna helix. These distortions provide recognition sites for enzymes catalyzing mismatch repair. Repair enzymes move along the double helix, scanning for dna situations.
