Final answer:
RecA binding to CI repressor initiates the lytic cycle of λ phage, where host cell machinery is hijacked for phage replication, resulting in cell lysis.
Step-by-step explanation:
When RecA binds to CI repressor in the λ phage system, it triggers the cleavage of the CI repressor. This is part of a response to DNA damage in the host cell, such as that caused by phage infection.
The cleavage of CI repressor leads to the induction of the lytic cycle of λ phage, whereby the phage redirects the cell's machinery for its own replication and results in cell lysis to release new phage particles.
This process is a prokaryotic immune-like response to phage DNA, employing the CRISPR/Cas system to recognize and destroy foreign genetic elements.
The CRISPR/Cas system acts as a primitive adaptive immune system in bacteria. It records segments of invader DNA (such as that of a phage) in the form of 'spacer' sequences.
Upon re-exposure to the same phage, these sequences guide the Cas endonucleases to target and cleave the phage DNA, preventing its replication. In essence, the phage DNA is recognized, unwound, and ultimately destroyed, preventing a new round of phage infection.
This activates the CRISPR/Cas system, which functions as a bacterial immune response to eliminate invading phage DNA.