LIFESCI 3 Lecture Notes - Lecture 14: Pyrimidine Dimer, 6-O-Methylguanine, Coal Tar
Document Summary
Dna damage: 2 general job for cell in repairing damage: Identifying damage: properly repairing damage, 3 different types of spontaneous dna damage, 1. ) Hydrolysis of glycosidic bond: spontaneous deamination of 5-methlycytosine generates thymine. Will not be recognized as abnormal base. Can lead to transition mutation if unrepaired: 2. ) Incapable of base pairing: pyrimidine dimers interfere with dna replication & transcription, covalently connecting 2 pyrimidines, consequence: pyrimidine dimer distorts the helix --> the bases in the dimer no longer participates in h-bonding, 3. ) Methylation of guanine to will mispair o6-methylguanine with thymine. After additional dna replication, this will lead to a g:c to a:t transition mutation: b. double-strand breaks (dsbs) in dna backbone. Ionizing radiation can cause dsbs in dna backbone. Lesions that block replication fork can lead to cell death if not repaired. Nicks in 2 strands fragment both daughter chromosomes: benzopyrene = known carcinogen in smoke of burning cigs, wood, and coal tar.
