Final answer:
The entry stage of the viral replication cycle is essential for unenveloped viruses; it involves the viral nucleic acid entering the host cell to begin replication. Enveloped viruses can enter through endocytosis or membrane fusion. Afterward, the virus replicates, assembles, and exits the host cell to continue the infection cycle.
Step-by-step explanation:
Viral Replication Cycle: Entry Stage
The entry process of a virus into a host cell is a critical step in the viral replication cycle. For unenveloped viruses like bacteriophages, the entry is characterized by the release of the nucleic acid into the host cell, leaving the capsid outside. In the case of plant and animal viruses, the common entry method is endocytosis, where the virus is engulfed by the cell membrane. Some enveloped viruses have the ability to fuse their envelope with the cell membrane to gain entry. Once the virus is inside, it uncoats and releases its nucleic acid, which then undergoes replication and transcription.
The stages that follow involve the replication of viral components, assembly of new virions, and eventually, their ejection from the host cell to infect other cells. Egress can occur through cell death or a process known as budding, where new virions are wrapped in the host cell's membrane and extruded without immediate cell death.