Which sequence describes the lytic cycle of a bacteriophage?

• A. Phage integrates into host genome and remains dormant
• B. Phage attaches to bacterium, injects DNA, replicates, assembles progeny phages, and lyses the cell to release them
• C. Phage replicates without lysing the host
• D. Phage buds from the host cell without killing it

Answer: (B)

The lytic cycle is a rapid, destructive replication of a phage that ends with host cell lysis. It starts when the phage attaches to the bacterial surface and injects its DNA. The phage DNA then hijacks the host’s machinery to replicate the viral genome and synthesize phage proteins, followed by assembly of new phage particles. Finally, enzymes produced by the phage break down the cell wall, causing the cell to burst and release the progeny phages to infect more bacteria. This sequence—attachment, DNA injection, replication and assembly, then lysis—is characteristic of the lytic cycle. The other descriptions correspond to non-lytic processes or dormancy (integration into the host genome and later induction) or non-lethal release, which do not define the lytic cycle.