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To enter the cells, proteins on the surface of the virus interact with proteins of the cell. Attachment, or adsorption, occurs between the viral particle and the host cell membrane. A hole forms in the cell membrane, then the virus particle or its genetic contents are released into the host cell, where replication of the viral genome may commence.
In the lytic cycle, the viral DNA exists as a separate free floating molecule within the bacterial cell, and replicates separately from the host bacterial DNA, whereas in the lysogenic cycle, the viral DNA is integrated into the host genome. This is the key difference between the lytic and lysogenic cycles.
The fourth step in the viral cycle is replication, which is defined by the rapid production of the viral genome. How a virus undergoes replication relies on the type of genetic material the virus possesses. Based on their genetic material, viruses will hijack the corresponding cellular machinery for said genetic material.
Virus latency (or viral latency) is the ability of a pathogenic virus to lie dormant within a cell, denoted as the lysogenic part of the viral life cycle. [1] A latent viral infection is a type of persistent viral infection which is distinguished from a chronic viral infection. Latency is the phase in certain viruses' life cycles in which ...
The herpes virus can then exit this dormant stage and re-enter the lytic cycle, causing disease symptoms. Thus, while herpes viruses can enter both the lytic and lysogenic cycles, latency allows the virus to survive and evade detection by the immune system due to low viral gene expression. The model organism for studying lysogeny is the lambda ...
A typical virus replication cycle Some bacteriophages inject their genomes into bacterial cells (not to scale) Viral populations do not grow through cell division, because they are acellular. Instead, they use the machinery and metabolism of a host cell to produce multiple copies of themselves, and they assemble in the cell. [ 74 ]
The genome remains inserted into the host genome in a dormant state. The prophage is duplicated with every subsequent cell division of the host. The phage genes expressed in this dormant state code for proteins that repress expression of other phage genes (such as the structural and lysis genes) in order to prevent entry into the lytic cycle.
Life-cycle of a typical virus (left to right); following infection of a cell by a single virus, hundreds of offspring are released. When a virus infects a cell, the virus forces it to make thousands more viruses. It does this by making the cell copy the virus's DNA or RNA, making viral proteins, which all assemble to form new virus particles. [37]