Damage Tolerance Function can allow DNA replication to continue despite presence of DNA damage (e.g. thymidine dimer) Process DNA polymerase stalls at dimer sliding clamp releases regular DNA polymerase and binds the one of two translesion polymerases login to view 4 more bullets Mismatch Repair Process repairs G/T or A/C pairing login to view 1 more bullet involves MutS, MutH, MutL enzymes strand specific login to view 1 more bullet Deficiency hereditary nonpolyposis colorectal cancer login to view 13 more bullets Base Excision Repair Function specific endonucleases (glycosylases) remove bases that have been modified by several common mechanisms of damage login to view 1 more bullet can take place anytime during the cell cycle but occurs primarily in G1 Process glycosylase specific for the damaged nucleotide removed damaged base by breaking glycosidic bond damaged base removed login to view 2 more bullets gap filled by DNA polymerase I login to view 1 more bullet ligation of strand nick by DNA ligase III Nucleotide Excision Repair Function removes thymidine dimers caused by UV-B light removes damaged bases caused by chemicals Process maintenance repair login to view 4 more bullets transcription-coupled repair login to view 3 more bullets Deficiency xeroderma pigmentosum (XP) login to view 11 more bullets Cockayne syndrome login to view 8 more bullets Homologous Recombination Function repair double-strand breaks requires a sister chromatid to use as a template login to view 1 more bullet Process double-strand break recognized by MRN complex BRCA and BLM enzymes involved in end processing Holliday junctions are formed login to view 1 more bullet junctions are resolved login to view 2 more bullets Deficiency Bloom syndrome login to view 7 more bullets BRCA-1 involved in login to view 1 more bullet BRCA-2 involved in login to view 1 more bullet Non-Homologous End Joining Function repair double-strand breaks login to view 2 more bullets occurs when a sister chromatid is not available to use as a template (prior to S phase of cell cycle) Process break recognized by MRN complex additional enzymes (Artemis, XLF, Pol μ) cut ends so they can bind DNA ligase IV joins ends together Deficiency severe combined immunodeficiency disease (SCID) login to view 1 more bullet