BSC 310 Lecture Notes - Lecture 38: Helicase, Streptococcus, Virus
22 Mar 2016
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Document Summary
There are 2 main categories of mutagenic electromagnetic radiation: Nonionizing- includes uv; purine and pyrimidine bases strongly absorb radiation, producing direct damage to dna such as pyrimidine dimers. Ionizing- includes x-rays, cosmic rays, and gamma rays; produce free radicals that damage macromolecules in cells, can fragment. Lesions on template dna can stall dna replication, which is lethal. Stalled replication, as well as other major dna damage, activate the. Sos system initiates various dna repair processes, some are error- free and others are error-prone as they do not require a template (cid:1) Error-prone methods allow replication to proceed (survival) but organism has many mutations (cid:1) Sos system regulates transcription of about 40 genes involved in dna damage tolerance and repair (cid:1) In damage tolerance, lesions remain but are bypassed by special dna polymerases that perform translesion synthesis. In dna repair, 2 error prone dna polymerases are used.
