Which factor is necessary for maintaining lysogeny in lambda phage?

• Explanation:
-The C1 repressor protein is crucial for maintaining lysogeny (the dormant state of the phage integrated into the host genome) in lambda phage.
-It does this by binding to specific operator sites on the phage DNA, preventing the expression of genes involved in the lytic cycle (the active replication and release of new phages that results in host cell lysis).
-The C1 repressor essentially keeps the phage's lytic genes turned off, ensuring the phage remains dormant within the host.

🔑Key Points:
-Lambda repressor is both a negative and positive regulator of gene transcription.
-The operator region where lambda repressor binds consists of three regions – OR1, OR2, and OR3. 
-Lambda repressor binds to OR1 and OR2 and prevents the binding of RNA polymerase to the PR region. So, now the expression of Cro is inhibited from PR.
-OR3 region is still vacant and RNA polymerase binds to the PRM, and promotes the transcription of its own gene i.e., CI gene, to produce lambda repressor protein.