Describe the lytic and lysogenic cycles of a bacteriophage.

• A. Lytic: phage replicates and lyses the host; Lysogenic: phage DNA integrates into the host genome and is replicated with the host.
• B. Lytic: phage DNA integrates into host genome; Lysogenic: phage replicates and lyses the host.
• C. Both cycles involve the phage entering a dormant state without affecting the host.
• D. The lysogenic cycle immediately produces new phages that lyse the host.

Answer: (A)

Understanding how a bacteriophage reproduces through two distinct life cycles helps explain why one path ends with the host cell bursting, while the other hides the phage inside the host’s own DNA. In the lytic cycle, after infection the phage takes over the bacterial machinery to replicate its genome and assemble new phage particles, culminating in lysis of the host and release of many new virions. In the lysogenic cycle, phage DNA integrates into the bacterial chromosome as a prophage and is replicated along with the host’s genome during cell division; the phage remains dormant for a time and only later may switch to the lytic cycle under certain conditions.

That’s why the description stating the lytic cycle involves replication and host lysis and the lysogenic cycle involves integration into the host genome and replication with the host correctly captures the two processes. The other descriptions either swap the roles of the cycles, claim both are dormant, or say lysogeny immediately produces lytic particles, which isn’t accurate.