Microbiology Chapter 13
Which of the following terms is used to describe a viral RNA genome which cannot be immediately translated into protein?
(-) strand
Replication of temperate phages and lytic phages have these steps in common...
-Assembly -Attachment -Release -Biosynthesis of viral components -Genome entry
What do viroids have/do not have?
Have: nucleic acids Do not have: capsid, metabolic pathways, mitochondrion, envelope
___ infections are analogous to lysogenic infections by bacteriophages in that they involve a viral genome that is silent in the host cell
Latent
Which term is used to describe the protein layer that is sandwiched between the capsid and envelope in enveloped viruses?
Matrix
first viral proteins to be produced in the T4 lytic cycle
Protein to stop the bacterial RNA polyermase from recognizing bacterial promoters and nuclease to to digest the host DNA
Viroids are composed of naked ___ strands
RNA
A single vision could contain a genome of...
RNA only or DNA only
The M13 phage has a single-stranded DNA genome that is converted by host DNA polymerase to a double-stranded DNA molecule called the
Replicative form
What late proteins are produced of the T4 lytic cycle?
T4 capsomeres and T4 tail fibers
Which phage has the greatest likelihood of increasing the pathogenicity of a bacterium?
Temperate phage
A lysogen is...
a lysogenized bacterium
Two major categories of viral infections are...
actue and persistent
Which type of cell death do some viruses trigger as a means of being released?
apoptosis
Zoonotic viruses that are spread to humans by arthropods are classified as ___
arboviruses
The ____ stage of the T4 lytic cycle is marked by the formation of new phage particles inside of the host cell
assembly
enveloped viruses are released by ___, a process that extrudes them through the membrane of the host cell
budding
Enveloped viruses exit host cells by ____, naked viruses are released upon _____ of the host cell
budding, apoptosis
The monomer of a capsid is called a ____.
capsomer
Viruses spread by the fecal-oral route are called
enteric viruses
What type of viruses are released by budding?
enveloped viruses
In a lysogenized bacterium, ______ of the prophage results in a lytic infection
excision
This phage type causes productive infections that do not kill the host cell
filamentous
Most viral spike proteins bind to protein receptor molecules on the host cell that are classified as _____
glycoprotein
What are the molecules (receptors) that viral spikes attach to on the host cell typically composed of?
glycoproteins
What are some characteristics of mimiviruses?
have genes for polysaccharide synthesis, are very large, and can be infected by parasite viruses
Which are the two main criteria used in classifying viruses?
host range and genome structure
Which term is used to describe the capsid of a virus which has twenty equally spaced panels of capsomers, forming a symmetrical structure?
icosahedral
Through the process of phage _____, a prophage is excised and enters the lytic cycle
induction
The phage-encoded enzyme that catalyzes the insertion of phage DNA into the host chromosome is called ____
integrase
What directs the incorporation of phage DNA into a bacterial chromosome?
integrase
At minimum, all viruses are composed of...
nucleic acids and proteins
Where are most DNA viruses replicated within the host?
nucleus
____ Infections remain for years, or even the lifetime of the host, sometimes without any symptoms
persistant
Environmental samples such as sewage and soil are routinely assayed for phage particle numbers using a ____ assay
plaque
Circular clearings caused by phage-induced lysis in a bacterial lawn called
plaques
A ___ is a proteinaceous infectious agent associated with transmissible spongiform encephalopathy
prion
The concentration of infectious phage particles in a sample is called the...
titer
Bacteria that are lysogenized with phage may produce ___ that are harmful to the host
toxins
True or false: Lysogenic phages can increase the pathogenicity of their bacterial host?
true
Which term describes the process by which the viral nucleic acid is released from the protective protein coat?
uncoating
A single virus particle
virions
A particle of infective nucleic acid without a protein coat like that found in virus particles
viroid
Viruses that infect other viruses are called...
virophages
Reassortment of gene segments that encode viral surface proteins that are recognized by the immune system can result in a loss of the immune system's ability to recognize and respond to the virus.
Antigenic shift
what are two prion related diseases?
Bovine spongiform encephalopathy, creutzfeldt-jakob disease
What type of viruses are mimiviruses?
DNA
Which factor determines the mechanism by which an animal virus will enter its host cell?
Enveloped vs. naked
True or false: Most bacterial engulf bacteriophages as part of the phage replication strategy
False
A change in the phenotype of a lysogen as a consequence of genetic material carried by a prophage is called...
lysogenic conversion
___ phages enter the prophage stage, while ___ phages burst the host cell shortly after infection
lysogenic, lytic
Bacteria that carry a prophage are called _____
lysogens
In ____-strand RNA viral genomes, the RNA is not in a form ready for translation
minus
Viral infections that result in the formation of new virus particles are called ____ infections
productive
Phage DNA that is integrated into the bacterial host genome is called a
prophage
A minimum, viruses are composed of nucleic acid that is surrounded by a _____
protein coat
A ____ is an animal virus which remains silent while integrated in the host genome or replicating as a plasmid
provirus
A virus can only infect cells that have the ____ to which that virus specifically attaches
receptor
The ____ of RNA viruses lacks a proofreading capability and makes many mistakes compared to the polymerases of DNA viruses
replicase
The protection of lysogens against infection by the same phage is provided by the _____ protein that will bin to the operator on incoming phage DNA, preventing expression of the phage genes
repressor