Lytic cycle
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2008-06-13T15:18:27Z
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robot Adding: [[ko:용균성 생활사]] [r5534]
{{Unreferenced|date=March 2008}}
[[Image:Viral Reproduction Chart.png|300px|right]]The '''lytic cycle''' is one of the two cycles of [[virus|viral]] [[reproduction]], the other being the [[lysogenic cycle]]. These cycles should not, however, be seen as separate, but rather as somewhat interchangeable.{{Or|date=March 2008}} The lytic cycle is typically considered the main method of viral replication, since it results in the destruction of the infected [[cell (biology)|cell]].
==Description==
The lytic cycle is a four-stage cycle.
==='''Penetration'''===
To infect a cell, a virus must first enter the cell through the [[plasma membrane]] and (if present) the cell wall. Viruses do so by either attaching to a receptor on the cell's surface or by simple mechanical force. The virus then releases its genetic material (either single- or double-stranded [[RNA]] or [[DNA]]) into the cell. In doing, the cell is infected and can also be targeted by the immune system.
==='''Biosynthesis'''===
The virus' nucleic acid uses the host cell’s machinery to make large amounts of viral components. In the case of DNA viruses, the DNA [[Transcription (genetics)|transcribes]] itself into [[messenger RNA]] (mRNA) molecules that are then used to direct the cell's ribosomes. One of the first polypeptides to be translated is one that destroys the hosts' DNA. In [[retrovirus]]es (which inject an RNA strand), a unique enzyme called [[reverse transcriptase]] transcribes the viral RNA into DNA, which is then transcribed again into RNA.
===Maturation and lysis===
After many copies of viral components are made, they are assembled into complete viruses. The phage then directs production of an enzyme that breaks down the bacteria [[cell wall]] and allows fluid to enter. The cell eventually becomes filled with viruses (typically 100-200) and liquid, and bursts, or [[Viral lysis|lyses]]; thus giving the lytic cycle its name. The new viruses are then free to infect other cells.
====Lytic cycle without lysis====
Some viruses escape the host cell without bursting the cell membrane, but rather bud off from it by taking a portion of the membrane with them. Because it otherwise is characteristic of the lytic cycle in other steps, it still belongs to this category. [[HIV]], [[influenza]] and other viruses that infect eukaryotic organisms generally use this method.
[[Category:Virology]]
[[Category:Bacteriophages]]
[[Category:Microbiology]]
[[de:Lytischer Zyklus]]
[[ko:용균성 생활사]]
[[pl:Cykl lityczny]]
[[pt:Ciclo lítico]]