MGY377H1 Midterm: Study notes for midterm
Document Summary
Coordinated transcriptional regulatory system that enables cell to turn on different repair enzymes in response to dna damage. Involves: reca - protein that binds ssdna and facilitates dna recombination, lexa dna binding protein that represses transcription of a number of genes involved in dna repair. Under normal conditions, lexa repressor is abundant in cell, binds dna to keep levels of reca and uvrab and other genes low. When dna damage occurs, reca recruited to single stranded dna: lexa is cleaved, other genes that were repressed now induced. Positive feedback: lexa controls own expression, when damage is repaired, lexa shut down its own expression, turning off the response. Damage to dna if extensive, amount of lexa in cell will drop a lot. Activate expression of polymerase like umucd that can copy even damaged templates by guessing what the correct sequence is: lots of errors introduced. Alteration in base structure that is not repairable. Activation of prophages into lytic cycle ***