SOS system E.coli

Question 1

what is the SOS system in E.coli

Answer 1

stress response to DNA damage

Question 2

what is the name of the group of genes in E.coli which are under the control of the same regulator?

Answer 2

regulon

Question 3

what is the name of the repressor in the regulon? and where is it?

Answer 3

LexA is spread over the ch, in different positions

Question 4

explain how the SOS system in |E.coli is activated.

Answer 4

1) external or internal stress on DNA
2) causes double-strand break
3) RecBCD cleavage, rec A loaded and forms a recA-ssDNA filament which acts on lexA
4) rec A acts as a protease and degrades lexA
5) less lex A present, facilitating access to RNA pol–> causing transcription
6) continued gene activation until repaired

Question 5

explain the SOS system feedback loop, regarding rec A and lex A

Answer 5

increased rec A will lead to decreased lexA and DNA repaired, then recA is decreased once repaired and lex A increased to inactivate SOS system and this goes on when damage is present.