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63 terms

Micro

chapter 13
STUDY
PLAY
protection and recognition
The outermost layer of a virion fulfills what functions of the virus?
nucleic acid
During the intracellular state, a virus exists as
type of nucleic acid
Viruses are primarily classified according to their
interactions
Host specificity of a virus is due to
envelope
What would NOT be found as a component of a bacteriophage?
in both cells and viruses
A lipid membrane is present
both cells and viruses
Double-stranded DNA genomes are found in
cells only
Cytoplasm is a characteristic of
true
Most viruses cannot be seen by light microscopy. TRUE OR FALSE
true
Protozoa are susceptible to viral attack. TRUE OR FALSE
they require a host to reproduce
How are viruses different from cells?
package and protect the viral genome
What is the function of the structural elements of a virus?
a prophage
Lysogenic viral DNA integrating into the host genome is referred to as
exposure to UV light
what event might trigger induction of a temperate bacteriophage?
host cell dies during lytic stage
How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?
copied every time the host DNA replicates
What is the fate of the prophage during the lysogenic stage?
penetration
In which stage is the viral DNA introduced into the cell?
assembly
In which stage does formation of mature viruses occur?
biosynthesis
The host DNA is usually degraded during which stage?
virus would not infect the new host
What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?
lysogenic conversion
Bacteriophage genes that cause toxin production in a normally harmless bacterial species are an example of _____.
the infected cell may live for a long time
Infections with enveloped animal viruses are similar to lysogenic phage infections because _____.
entry and release
Lysozyme is important for which of the following stages of lytic replication in bacteriophage T4?
UV light and X rays
What agent is capable of inducing conversion of a prophage back to a lytic phage?
prusiner
Which of the following individuals discovered prions?
virion
what is a virus in the extracellular state?
plant
The first virus to be identified was isolated from a _____.
protein
The capsid of a virus is made out of which of the following types of molecules?
prion
does NOT refer to viral shapes
dependent on host cell
Why do viruses have to infect host cells?
attachment
The tail fibers of a bacteriophage are most useful during which of the following stages of the lytic replication cycle?
viral DNA
Which of the following is a major difference between a lysogenic and a lytic cycle in bacteriophages?
retroviruses
What viruse creates a DNA intermediary molecule from the information in their RNA genomes?
herpesviruses
What types of viruse replicates in the cell's nucleus?
rna dependent
What type of viruses replicates in the cell's nucleus?
cytoplasmic membrane
Bacteriophages can use all of the following structures for attachment to a bacterial cell EXCEPT _____.
envelope
A naked virus is one without _____.
uncoating
Each of the following features is common to BOTH bacteriophage AND animal virus infections EXCEPT __________.
phage persists
Each of the following features is common to BOTH bacteriophage AND animal virus infections EXCEPT __________.
cancer causing viruses
In the early 1900s, the virologist F. Peyton Rous discovered _____.
allow bacteriophages to become latent
Fertilized chicken eggs are useful for the culture of viruses for all of the following reasons EXCEPT _____.
continuous
HeLa cells are an example of a __________ cell culture.
contain no nucleic acid
Scientists have determined that prion diseases are not caused by a type of slow virus because prions _____.
true
Viruses have genomes of DNA or RNA, but never both. TRUE OR FALSE
true
Viruses can specifically infect one type of cell within an organism. TRUE OR FALSE
true
Bacteriophages outnumber all known life forms. TRUE OR FALSE
false
According to the ICTV scheme of classification, viruses can be classified by a variety of characteristics, including the diseases they cause. TRUE OR FALSE
true
Proviruses become a permanent part of the host cell's genome. TRUE OR FALSE
true
Bacteriophages can be used in place of antibiotics to treat certain bacterial diseases. TRUE OR FALSE
true
Lysogenic bacteriophages can be excised from the chromosome by any agent that damages the cell's DNA. TRUE OR FALSE
false
Retroviruses need RNA-dependent RNA transcriptase to replicate themselves. TRUE OR FALSE
false
Diploid cell cultures have an unlimited life span. TRUE OR FALSE
false
The destruction of chickens and other domesticated fowl prevents the spread of avian influenza. TRUE OR FALSE
false
An infection in which a host cell sheds new viruses slowly and steadily is called a latent infection. TRUE OR FALSE
spongiform encephalopathies
As a group, prion diseases are more formally known as _____.
true
An icosahedral capsid is the most common type of polyhedral capsid and is also found in bacteriophage. TRUE OR FALSE
viroids
Small, circular RNA molecules that are infectious to plants are called _____.
false
Viruses are classified into kingdoms and divisions, just like bacteria and eukaryotes.
induction
A prophage is excised from the host chromosome and viral replication proceeds in a process called _____.
false
The viral envelope contains phospholipids and proteins, all of which originate from the host membrane.
assembly
Which step in the viral life cycle is usually a spontaneous process, but is sometimes controlled by viral enzymes?
false
If neoplasia occurs, this means that cancer will follow. TRUE OR FALSE
host membrane merges
What is the main difference between membrane fusion and endocytosis?