Final answer:
RecA is a protein that aids in repairing double-stranded DNA breaks through Homologous Recombination, and LexA regulates the SOS response in bacteria, ensuring the expression of DNA repair proteins. Together, they maintain genomic integrity after damage occurs.
Step-by-step explanation:
The roles of RecA and LexA are crucial in the context of DNA repair. RecA, an evolutionarily conserved protein found as RadA in Archaea and Rad51 in Eukaryotes, is central to the process of Homologous Recombination, a complex DNA repair pathway. In DNA repair, RecA proteins bind to single-stranded DNA to form a nucleoprotein filament that searches for homologous sequences in a replicating DNA strand, facilitating the repair of double-stranded breaks by aligning and pairing with the homologous DNA and allowing replication to continue accurately without deletions or insertions.
LexA, on the other hand, is a repressor protein that regulates the SOS response, a global response to DNA damage in bacteria. Upon DNA damage, RecA binds to single-stranded DNA and stimulates the autoproteolytic activity of LexA, causing it to cleave itself and derepress the SOS genes, which then transcribe proteins necessary for DNA repair. The integrated activity of RecA and LexA thus maintains genomic integrity after damage by triggering the bacterial SOS response and facilitating homologous recombination repair mechanisms.