Once inside a cell, the virus releases its DNA or RNA (which contains the information needed to create new virus particles) and takes control of some aspects of the cell's metabolism. The components of the virus are then manufactured inside the cell and must be properly assembled for the virus to be released and remain infectious.
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When a viral DNA enters a host cell, it can integrate into the host cell's DNA. This integration can lead to the host cell producing viral proteins, which can result in the replication and spread of the virus.
In the lytic cycle, the viral DNA can maintain a separate existence from the host DNA, but the host DNA replicates the viral DNA. The replicated viruses eventually become so numerous that the cell bursts releasing the new viruses which can then affect more cells. Another viral mechanism, the lysogenic cycle, involves combining the viral DNA with the host DNA, which will be passed on to daughter cells during cell reproduction. Eventually, during unfavorable, conditions, the lytic cycle will occur, and the infected cells will start replicating viruses, which will then eventually cause the cell to burst, releasing the new viruses.
The process is performed by reversed transcriptase protein and is called reverse transcription.
The viral DNA that is embedded in a host's DNA is called a provirus.
In lysogenic infection, the virus integrates its genetic material into the host cell's DNA and replicates along with the cell. The host cell continues to divide and function normally, unaware of the viral DNA present. Over time or upon activation, the integrated viral DNA can switch to the lytic cycle, causing the cell to produce new virus particles and ultimately lyse (burst) to release them.
The three stages of lysogenic infection are attachment, insertion (integration) of viral DNA into host DNA, and replication of the viral DNA along with host DNA.
Attachment: HIV binds to host cell receptor. Entry: HIV enters host cell. Reverse transcription: Viral RNA is converted into DNA by reverse transcriptase. Integration: Viral DNA is integrated into host cell DNA. Transcription: Viral DNA is transcribed into RNA. Translation: Viral RNA is translated into viral proteins. Assembly: New viral particles are assembled. Budding: Newly formed viruses bud off from host cell.
In a lytic infection, the virus enters the host cell, takes over the cell machinery to replicate itself, and then destroys the host cell to release new viral particles. In contrast, in a lysogenic infection, the viral DNA integrates into the host cell's DNA and remains dormant without causing immediate harm; the viral DNA can be activated to enter the lytic cycle under certain conditions.