1. SOS response in E. coli By Dan Wilson

2. SOS response in E. coli  The bacterium is exposed to something that damages its DNA. For example: Radiation or some type of mutagen that will damage the bacterial DNA.  After damage occurs lesions will appear damaging sections of the DNA.

3. SOS response in E. coli If the damage is too great then normal repair mechanism may not be able to repair the damage. If there is not a lot of lesions then sometimes normal replication methods can repair the DNA DNA sequence is lost where there are lesions

4. SOS response in E. coli Damaged DNA Replicated DNA with top strand DNA replicated with damaged strand.

5. SOS response in E. coli Two key proteins involved in the response are LexA and RecA. LexA is a repressor protein under normal conditions and inhibit the SOS response RecA when the DNA is damaged this protein inactivates the LexA protein cleaving it and this triggers the SOS response.

6. SOS response in E. coli If the lesions are more widespread then the SOS response is used. During DNA replication when DNA polymerase gets to the damaged spot it basically give its best guess as to what the missing DNA sequence should be.

7. SOS response in E. coli This system is far from perfect and mutations can occur. Mutations…. Antibiotic resistance.

8. Works Cited Campbell, M., & Farrell, S. (2012). Biochemistry. Belmont California: Brooks/Cole. Page 271 Friedman, N., Vardi, S., Ronen, M., Alon, U., & Stavans, J. (2005). Precise temporal modulation in the response of the SOS DNA repair network in individual bacteria. Plos Biology, 3(7), e238 : http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=15 954802&site=eds-live http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=15 954802&site=eds-live Michel, B. (2005). After 30 years of study, the bacterial sos response still surprises us. Plos Biology, Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1174825/ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1174825/