Question

1) The SOS regulatory system is activated by _________________.

a.	repression of RecA

b.	the activity of DNA polymerase IV

c.	DNA damage

d.	transcription of LexA

2) During an infection of a host cell with a lytic virus, viral mRNA and proteins are synthesized in what phase of viral replication?

a.	Latent period

b.	Burst period

c.

Lag phase

d.	Exponential growth

e.	Attachment

3) A CRISPR system is a_______________________________________.

a.	none of these answers are correct

b.	DNA repair mechanism

c.	protein chaperone

d.	prokaryotic immune system that preserves genome stability

Answer 1

Answer of question 1--- (c) DNA damage

Explanation: The SOS response is a response to DNA damage that leads to the arresting of cell cycle and DNA repair and mutagenesis is induced. The SOS response machinery involves RecA protein which get activated by single stranded DNA. Basically, because of the DNA damage, accumulation of single stranded DNA occurs at replication forks that would ultimately blocks the DNA polymerase. Finally, RecA forms a filament around the single stranded region and gets activated.