Chapter 17 Flashcards
Virus
An infectious particle consisting of little more than genes packages in a protein coat but can not reproduce or carry out metabolism outside of a host.
Can have single or double stranded DNA
Capsid
Protein she’ll enclosing the viral genome
Viral envelope
A membrane, derived from membranes of the shot cell, that cloak the capsid which in turn enclosed a viral genome
Bacteriophages
Virus that infects bacteria
Host range
Range of species a virus can use as a host
Lytic cycle
Virulent phage
A phase replicative cycle that culminates in death of the host cell by lysing a bacterium and releasing phases produced by the cell
Phage produced by lytic cycle
Lysogenic cycle
Template phages
Allows replication of the phage genome without destroying the host. Environmental signal triggers cell to induce lytic cycle
Phages capable of both modes of replicating within a bacterium
Prophage
A phage genome that has been inserted into a specific site on a bacterial chromosome
3 types of single stranded RNA genomes found in viruses
- Viral genome directly serves as mRNA (positive sense)
- Rna gene serves instead as a template for mRNA synthesis (- sense)
- Retrovirus: an RNA virus that replicates by transmitting it’s RNA into DNA anD then inserting the DNA into a cellular chromosome (reverse transcriptase)
Provirus
A viral genome that is permanently inserted into a host genome
Epidemic vs, pandemic
Widespread outbreak
Global epidemic
Do virus’s have mutations?
RNA viruses have high rates of mutations because viral rna polymerase does not proofread.
Horizontal and vertical transmission
Horizontal- infect by external source of virus
Vertical- a plant inherited a viral infection from parent
How do plant viruses spread?
Through plasmodesmata
Prions
An infectious agent that is a misfolded version of a protein. Increase in number by converting correctly folded versions to more prions.
- act very slowly(incubate 10 years)
- virtually indestructible
- in brain causes neuronal damage and death.
