Correct option is C
The SOS response is a regulatory network in E. coli that is activated upon DNA damage. It involves:
- RecA protein: Acts as a sensor for DNA damage.
- LexA repressor: Suppresses SOS genes under normal conditions.
- Translesion DNA polymerases: Help bypass DNA lesions.
Evaluating the Statements
Statement A: "RecA-DNA filament complex stimulates the autoproteolytic activity of the LexA repressor."
- Correct.
- When DNA damage occurs, RecA binds to single-stranded DNA (ssDNA) regions, forming a RecA-DNA filament.
- This complex induces the self-cleavage (autoproteolysis) of LexA, leading to SOS gene activation.
Statement B: "RecA is activated due to the blunt ends of double-strand breaks caused by DNA damage-inducing agents."
- Incorrect.
- RecA is activated by single-stranded DNA (ssDNA) regions, not blunt-ended double-strand breaks.
- It coats the ssDNA generated from stalled replication forks or other repair mechanisms.
Statement C: "The SOS response includes the activation of synthesis of translesion polymerases."
- Correct.
- The SOS response upregulates translesion DNA polymerases (Pol IV and Pol V), allowing replication across damaged DNA.
Statement D: "The destruction of LexA promotes synthesis of photolyase, which acts along with RecA to reverse the pyrimidine dimer formation process."
- Incorrect.
- Photolyase is not part of the SOS response.
- It is involved in direct DNA repair via photoreactivation, but the SOS response primarily promotes nucleotide excision repair (NER) and translesion synthesis.
Correct Answer:
- A and C are correct.
- Option 3 (A and C).
