Chapter 6
The final step in T2 bacteriophage infection results in
lysis of the bacterial cell and release of new viral particles.
Corynebacterium diphtheriae is made virulent by incorporated prophage genes encoding the diphtheria toxin. What term describes this process?
lysogenic conversion
Visible, clear, well-defined patches in a monolayer of virus-infected cells in a culture are called
lysogeny.
Why couldn't the avian influenza outbreak be stopped in 2015?
migratory birds repeatedly introduced the virus into healthy flocks.
"Asian" influenza viruses are found in the United States primarily because
migratory birds transmit the virus to domestic flocks.
The severity of symptoms of a specific strain of influenza often correlates to how deeply the virus penetrates the respiratory tract. The viral component most responsible for this aspect of infection would be the _____.
neuraminidase spikes
Once inside the host cell, viral DNA directs production of _______.
new viral particles
The correct order of the stages for phage replication are 1 Assembly 2 Attachment 3 Transcription/replication 4 Release 5 Penetration
2, 5, 3, 1, 4
Please match the statement to the term that it most accurately describes to test your understanding of the detection of viral infections.
Polymerase chain reaction Amplification of viral nucleic acid from a patient sample Cell culture, embryo, animals Takes a long time to get diagnosis Rapid tests Detect virus or cytopathic effects in cells or tissue Screening Detection via antibodies in the patient's blood
Which of the following viruses did D. Ivanowski and M. Beijerinck work with?
Tobacco Mosaic Virus (TMV)
If the virus is present as a provirus in the host cell, it remains latent and never produces new virus.
True
The polygenic mRNA codes for making one long polyprotein, which is then cleaved into the separate individual virus proteins.
True
Please select all the accurate statements about the importance of prions and viroids and the diseases they cause.
Viroids pose significant problems in many economically important crops. Prions induce abnormal folding in normal proteins. Prion infections have long latent periods.
The capsid of a virus is
a protein shell that surrounds the nucleic acid.
Creutzfeldt-Jakob disease is
a spongiform encephalopathy of humans.
The general steps in viral replication (in order) are
adsorption, penetration, synthesis, assembly, release.
Which is incorrect about prophages?
always lyse the host cells
Please select all of the following that represent viral characteristics.
are obligate intracellular parasites have a 20 to 450 nanometer diameter are composed of a capsid surrounding a nucleic acid core
The stage of T4 replication that involves the protein fibers on the phage and receptors on the bacterial cell wall is the
attachment stage.
The provirus state exists when
double-stranded viral DNA is integrated into host cell chromosome.
Which of the following viral types enter animal cells via fusion with the animal cell membrane?
enveloped viruses
The three basic groups of viruses based on morphology include
enveloped viruses, non enveloped viruses, and complex viruses.
The use of antibiotics is an effective treatment for viral infections.
false
Which of the following are the most useful using modern systems to classify a newly discovered virus?
genome is RNA envelope contains particular spike proteins
The inability of the HPAI H5N2 flu to move successfully from birds to humans is primarily attributable to
hemagglutinin proteins.
When a virus is noninfectious it is termed __________.
inactive
Which of the following is a type of cytopathic effect?
inclusions in the nucleus multinucleated giant cells inclusions in the cytoplasm rounding of cells
Label the six major stages of an animal virus replication cycle.
Adsorption Penetration Uncoating Synthesis Assembly Release
The T-even bacteriophages such as T2 and T4 infect
Escherichia coli.
Enveloped viruses are usually released from the host cell by exocytosis.
False
Which of the following represents a virus family name?
Herpesviridae
If the DNA of the provirus is transcribed
one long polygenic mRNA is produced.
In phage replication
only the phage protein enters the bacterial cell.
A major difference in the replication of animal viruses and bacteriophages is the ______ step.
penetration
The stage of T4 replication that involves the injection of phage DNA is the
penetration stage.
A prophage is
phage DNA integrated into host cell genome
In the lytic cycle of phage replication
phage nucleic acid is replicated and phage genes are expressed, making new phage protein and lysing the host cell.
What tool or technique used by Ivanowski and Beijerinck while studying diseased tobacco plants enabled them to determine that the disease was caused by an agent significantly smaller than bacteria?
porcelain filters that trapped bacteria but allowed passage of the virus
All viruses
possess a capsid composed of protein. are reliant on a host cell for their own reproduction.
Noncellular infectious protein particles are called
prions.
In the attachment step of phage replication
protein fibers in the phage tail attach to specific receptors on the bacterial cell wall.
The "H" and "N" designations for influenza viruses refer to
receptor spikes.
Viruses acquire envelopes around their nucleocapsids during
release
A bacteriophage initially associates with which bacterial structure?
the bacterial cell wall
Antigenic shift is a direct consequence of
the influenza virus carrying its genetic information on separate strands of RNA.
When used in a description of viruses, the term replication includes
the production of multiple copies of a virus by a host cell. the copying of the viral DNA in a DNA virus. the copying of the genomic RNA in an RNA virus.
The primary purposes of viral cultivation include
to isolate and identify viruses in clinical specimens. to research viral structure, multiplication, genetics, and effects on host cells. to prepare viruses for vaccines.
The stage of T4 replication that involves the copying of the phage DNA and the synthesis of various phage proteins is the
transcription stage.
Prions are responsible for
transmissible spongiform encephalopathies Mad Cow disease. Creutzfeldt-Jakob disease.
A portion of the viral envelope comes from the cell membrane of the host cell.
true
Bacteriophage DNA directs the degradation of the bacterial host cell's DNA.
true
Retroviruses have
two copies of single-stranded RNA
Please select the characteristics that are used to identify and name viruses.
type of capsid type of envelope nucleic acid strand number area of the host cell in which the virus multiplies
Host range is limited by the
type of host cell receptors on cell membrane.
Which of the following can cause a phage in the lysogenic stage to revert to the lytic stage?
ultraviolet light
The first event to occur is
viral spike proteins are inserted into host cell membrane.
All of the following are correct about treating viral diseases except
viruses are killed by the same antibiotics that kill bacteria.
Please match the viral culture method with the statement that most accurately describes it to test your understanding of the various methods for growing viruses.
1. Cell culture Available for viruses with specific host ranges 2. Bird embryos Self-contained unit with its own sterile environment and nourishment 3. Live animals Allows for viral effects on the whole organism to be observed
The viral _____ is responsible for introducing the viral DNA or RNA into the cell.
Capsid
Rank the following viruses from smallest to largest
Influenza-3 Megavirus-6 Phage T2-2 Herpes-4 Poxvirus-5 Yellow Fever-1
The viral capsid
becomes completely enclosed by the region of the cell membrane into which the spikes and matrix protein are embedded.
Enveloped viruses are usually released from the host cell by
budding.
Please select criteria that are used to classify viruses.
capsid structure presence/absence of an envelope genetic makeup
Viral capsids are made from subunits called
capsomeres