Download Virus information

Virus information
DNA/RNA=complex molecules that tell cells how to build proteins
Gene: a sequence of the DNA/RNA that specifies one protein
Virus replication= making copies of the virus
Viral replication can only occur in a living cell, prokaryotic or eukaryotic
Viruses that infect bacteria (prokaryotic) are called bacteriophage
Viral replication is called the lytic cycle
1.attachment to host cell
2.injection/transmission of DNA or RNA into host cell
3. copying of DNA or RNA, or cutting of host DNA
4.building proteins to make coat of the virus
5. viral assembly
6. lysis, viruses rupture the host cell
7. infection of neighboring cells
Changes in the DNA or RNA are called mutations
The smaller the amount of DNA/RNA the easier it is to change, and produce new proteins and new virus
characteristics
DNA viruses have mechanisms to repair mutations, therefore they are slower to change
RNA viruses lack error-checking mechanisms, thus they change faster
When the cell is infected it loses its ability to work and eventually dies (lysis). Viral infections in organs
of multicelled organisms cause diseases (pathogenicity). Ex. Tuberculosis, influenza, HIV
Transduction: in bacteria, occurs when DNA is transferred from one host cell to another by the virus.
When the virus replicates inside the host it may incorporate some of the host DNA in its own DNA, or
some of the host DNA inside its protein coat when it is assembled. This will then be transferred to the
next host cell and could be incorporated into that host cell’s DNA. (Virus acts as a vector)
Lysogenic cycle: when the lysis of the host cell is delayed (latent). This can occur when the viral DNA is
spliced into the host DNA and often does not initially impair the function of the DNA or its host. The
host cell often acquires new properties and can continue to reproduce producing new cells with the
altered DNA until the viral DNA becomes active and then destroys the host cell, manifesting the
infection and the individual finally shows symptoms of the disease.