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