Attachment, Penetration, and Uncoating
Many of the viruses that infect humans are DNA viruses, including the viruses that cause herpes and smallpox. Like all viruses, these infectious agents search for host cells with specific characteristics. When a virus has located an acceptable host cell, it attaches itself to the cell. This is the first step, called attachment. After attachment, the virus penetrates the cell and goes through a process called "uncoating." Viruses have a protective coat of proteins called a capsid layer. During uncoating, this layer is removed, and the virus’ DNA is released into the cell. Attachment, penetration, and uncoating are the three fundamental first steps in virus replication.
Transcription and Translation
After uncoating, the host cell begins the process of replicating the virus. Normally, cells divide and reproduce by copying their own genetic material and making new versions of themselves. However, when a virus has inserted its own DNA into a host cell, the cell will begin copying that DNA (along with some enzymes that the virus requires) instead, making new virus. Thus, the virus co-opts the reproductive mechanism of the cell for its own replication. When the host cell finds the virus DNA, it begins to copy the DNA through a process called transcription and translation. This complicated process involves the organs of the cell and free amino acids. The result is a copy of the virus DNA, as well as copies of proteins that are needed to put the new viruses together with their own capsid layers.
Lytic and Lysogenic Cycles
When the host cell has produced a completed virus, the new virus is released from the cell in a process called "lysis," and the new virus goes on to replicate itself in a different cell in the same manner. The DNA virus replication cycle described is called the lytic cycle. The lytic cycle is the most common method of virus replication, but there is another method called the lysogenic cycle. Although the two cycles are quite similar, the lysogenic cycle is more efficient. Whereas, in the lytic cycle, an infected cell replicates and releases a virus without reproducing itself, the lysogenic cycle allows infected cells to reproduce after they have been infected. The host cell copies itself along with the virus DNA, and the copies copy themselves, and so on. The result is a large number of infected cells, all of which will eventually create copies of the virus. Thus, one virus infecting one cell results in an enormous amount of new virus. Typically, the lysogenic cycle is used by bacteriophages rather than animal viruses.
Many of the viruses that infect humans are DNA viruses, including the viruses that cause herpes and smallpox. Like all viruses, these infectious agents search for host cells with specific characteristics. When a virus has located an acceptable host cell, it attaches itself to the cell. This is the first step, called attachment. After attachment, the virus penetrates the cell and goes through a process called "uncoating." Viruses have a protective coat of proteins called a capsid layer. During uncoating, this layer is removed, and the virus’ DNA is released into the cell. Attachment, penetration, and uncoating are the three fundamental first steps in virus replication.
Transcription and Translation
After uncoating, the host cell begins the process of replicating the virus. Normally, cells divide and reproduce by copying their own genetic material and making new versions of themselves. However, when a virus has inserted its own DNA into a host cell, the cell will begin copying that DNA (along with some enzymes that the virus requires) instead, making new virus. Thus, the virus co-opts the reproductive mechanism of the cell for its own replication. When the host cell finds the virus DNA, it begins to copy the DNA through a process called transcription and translation. This complicated process involves the organs of the cell and free amino acids. The result is a copy of the virus DNA, as well as copies of proteins that are needed to put the new viruses together with their own capsid layers.
Lytic and Lysogenic Cycles
When the host cell has produced a completed virus, the new virus is released from the cell in a process called "lysis," and the new virus goes on to replicate itself in a different cell in the same manner. The DNA virus replication cycle described is called the lytic cycle. The lytic cycle is the most common method of virus replication, but there is another method called the lysogenic cycle. Although the two cycles are quite similar, the lysogenic cycle is more efficient. Whereas, in the lytic cycle, an infected cell replicates and releases a virus without reproducing itself, the lysogenic cycle allows infected cells to reproduce after they have been infected. The host cell copies itself along with the virus DNA, and the copies copy themselves, and so on. The result is a large number of infected cells, all of which will eventually create copies of the virus. Thus, one virus infecting one cell results in an enormous amount of new virus. Typically, the lysogenic cycle is used by bacteriophages rather than animal viruses.
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