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