Although viruses differ in detail, their replication inside a host cell follows the same general sequence of stages:1. Attachment: viral proteins bind to specific receptors on the host cell.
2. Entry (penetration): the viral nucleic acid enters the cell, by injection, endocytosis or membrane fusion.
3. Replication and synthesis: the viral genome is copied many times, and viral genes are transcribed and translated by the host to make capsid proteins and enzymes.
4. Assembly: new nucleic acid and capsid proteins come together to form new virus particles.
5. Release: new virions leave the cell, either by bursting it (lysis) or by budding through the membrane, which gives enveloped viruses their envelope.After entry, a virus can follow one of two routes:The lytic pathway: the virus replicates immediately. The host cell makes new virus particles and then bursts, releasing them to infect other cells. The host cell is destroyed.The lysogenic pathway (latency): the viral genome does not replicate straight away. In phages it is inserted into the host chromosome as a prophage; in some animal viruses it stays in the nucleus in a latent form. It is copied along with the host DNA every time the cell divides, causing no harm. Later a trigger such as stress or UV light can make the virus leave this state and enter the lytic pathway.
2. Entry (penetration): the viral nucleic acid enters the cell, by injection, endocytosis or membrane fusion.
3. Replication and synthesis: the viral genome is copied many times, and viral genes are transcribed and translated by the host to make capsid proteins and enzymes.
4. Assembly: new nucleic acid and capsid proteins come together to form new virus particles.
5. Release: new virions leave the cell, either by bursting it (lysis) or by budding through the membrane, which gives enveloped viruses their envelope.After entry, a virus can follow one of two routes:The lytic pathway: the virus replicates immediately. The host cell makes new virus particles and then bursts, releasing them to infect other cells. The host cell is destroyed.The lysogenic pathway (latency): the viral genome does not replicate straight away. In phages it is inserted into the host chromosome as a prophage; in some animal viruses it stays in the nucleus in a latent form. It is copied along with the host DNA every time the cell divides, causing no harm. Later a trigger such as stress or UV light can make the virus leave this state and enter the lytic pathway.