in a T:A base pair, 5-bromouracil is incorporated across from an adenine prior to replication the adenine undergoes tautomeriza d. In an A:T base pair, oxoG is placed across from the A during replication Why is MutT so important? What occurs in cells lacking this enzyme? 33. How does DNA polymerase proofreading specifically recognize mispairs (by what mechanism)? 34. Define the roles of each in mismatch repair: MutS, MutL, and MutH, exonuclease nd targ siiripie c Che slic slow if the 5. How does E. coli distinguish between the old and new strand for mismatch repair -longer nelicases r target ( at contro oading nt in the ion, but clamp c Sliding clamp he slid is not factor 1l inte nus, sl es tha o. How do human cells distinguish between the old and new strand for mismatch repair? 37. What are the steps of base excision repair? Where does the glycosylase cleaver So. why does the OxoG failsafe system lead to more ATOD CG than CGeDAT transversions? tab S3. What are the steps of nucleotide excision repair in bacteria? Why are the bacteriál proteins in this pathway named "UV" and human proteins "XP"? 40. Which repair system is tightly coupled to transcription? Why is it important to repair damage sensed by RNA polymerase quickly? 41. What is translesion DNA synthesis and when is it used? Why is it a last resort? Does it repair ssDNA or dsDNA? 42. What are the steps of homologous recombination repair? Which proteins are involved in searching for homologous sequences and how do they function? THE 43. What are the steps of nonhomologous end joining? icati asly. ent i rok liffi fth Th 44. When is NHEJ used as a mechanism for DNA repair? Why is it a last resort? Does it repair ssDNA or dsDNA? 45. Describe the general steps needed for a cell to become cancerous. 46. How do mutations and chromosomal abnormalities affect proteins and lead to disease? 47. What role do cell cycle checkpoints have in cancer? 48. Define a tumor suppressor and oncogene and give an example of each. 49. Define the role of ATM in the cell and cancer. o activate HRR or UporyDNA damage, ATM decides whether to NHÈJ. Which is preferred and why?