microbiology HW 6
Which of the following is most likely to function as a viral receptor on a host cell surface?
-a protein always present on the cell surface -a protein important in normal cell function
Which two stages of viral replication occur after viral synthesis?
-assembly -release
Examples of viral ligands on bacterial and archaeal viruses include
-beard-like fiber clusters -tail fibers -claw-like structures
Select the two most common forms of viral release
-budding -lysis
Examples of viral receptors on bacterial cells include
-cell wall polysaccharides -flagella -teichoic acids
Select the two direct methods for counting viruses
-electron microscopy -immuno-fluorescence microscopy
Select the four cellular structures that can be the source of viral envelopes.
-endoplasmic reticulum -nuclear membrane -plasma membrane -golgi apparatus
Select the three methods used by viruses to gain entry into host cells.
-fusion of the viral envelope with host cell membrane -endocytosis of the virus into the cell -injection of viral nucleic acid into the cell
Select the two indirect methods for counting viruses.
-hemagglutination assay -plaque assay
Viral specificity for a host cell type is dependent on ___
-host receptor -viral ligand
Which two of the following have direct involvement with viral attachment?
-host receptor -viral ligand
Which two of the following techniques allow the cultivation of animal viruses?
-inoculating tissue culture with animal cells -inoculating fertilized chicken eggs
Which two of these eukaryotic cell endocytic pathways are used by some virions to enter the cell?
-macropinocytosis -clathrin-dependent endocytosis
Which two of the following components make up a viral nucleocapsid?
-nucleic acid -protein coat
Which two of the following viral activities occurs during "viral entry"?
-penetration -uncoating
Which two components make up a viral nucleocapsid?
-protein coat -nucleic acid
Which two of the following are correct descriptions of viroid structure?
-relatively short; about 250 to 400 nucleotides long -circular ssRNA
Select the three methods that would most likely be successful in cultivating (growing) a plant virus.
-rubbing a mixture of virus and an abrasive on whole plants -grafting part of an infected plant onto a healthy plant -inoculating a culture of protoplasts
A single virus could have which of the following genomes?
-ssDNA -dsRNA -dsDNA -ssRNA
The RNA of viroids encodes how many gene products?
0
Which of these viruses is considered naked?
A
Which of the following best defines a plaque-forming unit (PFU)?
A number of virions that generates a single plaque
Which of the following best defines a virulent phage?
A virus that always progresses to lysis of the infected cell
Which of the following best defines a temperate phage?
A virus that can integrate its genome into the host genome
What types of viruses can use endocytosis as a means of viral entry?
Both enveloped and naked viruses
Viroids are infectious agents that consist of ___
RNA only
Because their host cells typically lack the appropriate enzymes, which type of viruses always encode the enzymes needed to copy their genome?
RNA viruses
Which is NOT true about lysogenic bacteria?
They would normally stop dividing
Which of the following viral structures is composed of just the protein that surrounds the nucleic acid?
capsid
Plant viruses require ______ to infect the cell.
cell wall damage
The best definition of cytopathic effects caused by a viral infection of eukaryotic cells is ___
changes or abnormalities in infected cells that are distinct from lysis
Virally infected eukaryotic cells often show microscopic or macroscopic abnormalities that are generally called ___ effects
cytopathic
virally infected eukaryotic cells often show microscopic or macroscopic abnormalities that are generally called ___ effects
cytopathic
Which of the following best describes the normal mechanism of RNA silencing in eukaryotic cells?
detection and degradation of dsRNA
In contrast to viral genomic DNA, which may be dsDNA, ssDNA, dsRNA, or ssRNA, cellular genomes are always ___
dsDNA
The outer lipid membranous layer found surrounding some viruses is called the ___
envelope
Which of the following viral structures comes principally from the host cell?
envelope
Viruses with a lipid membrane are often called ____.
enveloped
True or false: The cell membrane is the only host cell structure from which enveloped viruses obtain their envelope
false
The energy for viral replication, gene expression, and nucleocapsid assembly comes from ___
host ATP
RNA viruses always encode the enzymes needed to replicate their genomes because ___
host cells typically do not have ways to make RNA from RNA templates
Budding is best described as ___
how enveloped viruses acquire their membranes
During T4 bacteriophage release, lysozyme will ___
hydrolyze the peptidoglycan cell wall
Because it measures an effect of a virus, rather than actually counting virions, a hemagglutination assay is considered to be ___
indirect
Oncoviruses are known for their ability to ___
induce cancer
When a change in conditions causes a prophage to begin synthesizing and assembling new virions, this is called ___
induction
An icosahedral capsid ___
is a regular polyhedron
A helical capsid ___
is shaped like a hollow tube with protein walls
A bacterial plaque assay requires the use of a ___
lawn of cells
A viral envelope is composed of primarily ___
lipids
Most viruses will leave a host cell by bursting the cell, a process called ___, or by pushing through the cell membrane while taking some of that membrane with it, a process called ___.
lysis; budding
Bacteria infected by temperate phages are called ___ bacteria.
lysogenic
The portion of the illustrated bacteriophage life cycle labeled B is termed ___
lysogenic
The relationship between a temperate phage and the host cell is called ___
lysogeny
When a temperate phage integrates its genome into a host genome, the relationship between the phage and the host is termed ___
lysogeny
The portion of the illustrated bacteriophage life cycle labeled A is termed _____.
lytic
What effect would lysozyme have on a eukaryotic cell?
none
The simplest viruses consist of nucleic acid surrounded by a protein coat. This composite structure of viral nucleic acid and protein is called a ___
nucleocapsid
The simplest viruses consist of nucleic acid surrounded by a protein coat. This composite structure of viral nucleic acid and protein is called a ______.
nucleocapsid
The main difference between virulent phage and temperate phage is that virulent phage ___
only have a lytic cycle
Inoculating protoplasts, tissue cultures, or whole organisms, or grafting a diseased part onto a healthy organism, are all methods used to cultivate _____ viruses.
plant
Viroids cause disease in what type of host?
plants
Viruses can be quantified using a lawn of cells and counting the number of "clear spots" where the cells were killed by viruses. This sort of assay is called a ___ assay.
plaque
One method of counting temperate viruses involves mixing the virus and susceptible cells on top of a solid medium. As each virus begins lysing more and more cells, holes can be visualized on top of the medium. The virus-induced holes are specifically called ___
plaques
The image shows the result of mixing bacteriophage T4 with E. coli and adding to a solid medium. The visible holes are called _____.
plaques
Viral envelopes can often give a collection of identical viruses variable shapes. Such viruses are referred to as ___
pleomorphic
Viruses that have a somewhat variable shape due to the viral envelope are called ___
pleomorphic
Infectious agents composed entirely of protein are called ___
prions
Kuru, Creutzfeldt-Jakob disease, fatal familial insomnia, and Gerstmann-Strassler-Scheinker syndrome are human disease caused by ___
prions
A host cell that contains a ___, the nucleic acid of a temperate phage, can divide many times.
prophage
The nucleic acid of a temperate phage that is either integrated into the host cell's genome, or remains free in the cytoplasm, is called a ___
prophage
Virus will attach to host cells via a viral ligand and a host ___
receptor
What term describes the host cell component that a virus will bind for attachment?
receptor
Which stage of virus replication is shown in the image?
release
Once a virus enters the cytoplasm of a host cell, it begins to _____.
replicate its genome
The viral-encoded proteins that project from a viral envelope surface are called ____.
spike proteins (or peplomers
This picture represents which of the following macromolecules?
ssRNA
What viral life cycle step generally occurs after the virus has uncoated?
synthesis
Bacteriophages that can integrate their genome into the host genome are called ___ phage
temperate
Bacteriophages that can integrate their genome into the host genome are called ___ phage.
temperate
Which of the following describe a bacteriophage that may lyse its host cell, or remain within the cell without lysing it?
temperate
Enveloped viruses gain their envelope from ___
the host cell membrane
The image shows the result of mixing bacteriophage T4 with E. coli and adding to a solid medium. The plaques, indicated by the arrow, represent _____.
viruses and lysed bacterial cells
Virus (e) in this image has a capsid with which sort of viral symmetry?
Complex
Which type of genome would seem simplest to replicate in a host cell?
DNA
Because viroids code for no enzymes of their own, it is believed that they are replicated by a normal host cell enzyme called ___
DNA-dependent RNA polymerase
What name is given to a viral capsid that is shaped like a hollow tube with protein walls?
Helical
What name is given to a viral capsid that is composed of 20 equilateral triangular protomer faces?
Icosahedral
Select the correct description of the prion protein known as PrPSC.
It is the abnormal form of PrPC, which is a normal cellular protein. PrPSC accumulates in the brain of animals with scrapie.
Fertilized chicken eggs are a good medium to grow ___
animal viruses
This image depicts which stage of T4 bacteriophage replication?
assembly
The function of viral spike proteins is to ___
attach to a host cell surface
When performing a viral plaque-forming assay and using the terminology "bacterial lawn", the word "lawn" refers to ___
bacterial cells virtually side-by-side, covering an agar plate
Viral symmetry that is both icosahedral and helical and possibly other symmetry is collectively referred to as ___ symmetry.
binal
Certain viruses can be counted using a hemagglutination assay, but this only works it the virus ___
binds to red blood cells
The specific process of an enveloped virus leaving the cell is called ___
budding
The protein coat that surrounds the viral nucleic acid is called the ___
capsid
Which of the following best describes viral tropism?
the specific cell type that a virus can infect
Some viruses infect specific tissue types but not others. This is called ____.
tropism
The results of virus titration using a plaque-forming assay are normally expressed in PFUs, or plaque-forming ___.
units
Spikes, or peplomers, are ___
virally-encoded proteins that project from the envelope surface
A complete virus particle is called a(n) ___
virion
A complete virus particle is referred to as a ____.
virion
An infectious agent composed of only RNA is called a(n) ___.
viroids
the study of viruses is termed ___
virology
Bacteriophages that always proceed to lyse the infected cell are called ___ phage
virulent
In the context of virus replication, fusion with the host cell membrane, injection of nucleic acid, and endocytosis are the three modes of ___
virus entry into host cells