Micro ch 5 CC and Hw
Enveloped viruses leave cell by
budding through host membrane
In vitro
cell or tissue culture of viruses
Viral lysozyme digests the host cell wall, releasing the newly made phage, and lysing the host cell in the release step.
true
Rather than developing more antiviral medications, what is a more common focus for researchers when it comes to viral disease?
vaccine development
Virus
"poison" found in every cell type and habitat
Gram staining of the patient's samples would help to identify which type of pathogens?
Bacteria
How does lysogeny affect humans?
Bacteria can become virulent due to phage genes, causing greater damage to infected human host.
Prions
Composed primarily of misfolded (aberrant) protein (no nucleic acid)
Order these steps of the lytic cycle. A. Assembly B. Penetration C. Lysis D. Synthesis E. Adsorption
E, B, D, A, C
Viroids
Virus-like agents that parasitize plants. About one-tenth the size of an average virus
Choose the statement that correctly explains why viruses are described as "filterable."
Viruses are able to pass through a filter because of their small size.
Why do antiviral medications often have side effects?
Viruses are intracellular pathogens, and therefore, there is often host cell damage with antiviral treatments
Viral spikes
attach specifically to host cell receptors
Of all infectious agents, which group has the most variety of drugs designed to treat infections?
bacteria
Enveloped viruses are usually released from the host cell by
budding
Nonenveloped viruses leave cell by
by cell lysis
Antibiotics would be effective against which of these infections? Check all that apply.
whooping cough, cholera, syphillis,
Antiviral drugs
Almost all antiviral drugs licensed so far have been designed to target one of the steps in the viral life cycle: Integrase inhibitor class of HIV drugs interrupts the ability of HIV genetic information to incorporate into the host cell DNA. Easier to develop vaccines to prevent viral diseases
The T-even bacteriophages such as T2 and T4 infect
E. coli
DNA viruses
Single-stranded (ss) or double-stranded (ds; linear or circular); Enter the host cell's nucleus and are replicated and assembled there
How are temperate phages replicated?
The phage is replicated along with the host cell's genome.
Select the three choices that are the primary purposes of cultivating viruses.
To isolate viruses from clinical specimens, To prepare viruses for vaccines, To research the biology of viruses
Viruses are acellular
True
Select the three methods that are used to cultivate viruses.
Use of cell culture techniques, Use of animal inoculation, Inoculation of embryonated eggs
Provirus
Viral DNA incorporated into the DNA of the host
Persistent infections
cell harbors the virus and is not immediately lysed: Can last from a few weeks to the remainder of the host's life Can remain latent in the cytoplasm
A naked virus fuses with the host cell membrane.
false
All viruses leave a cell by exocytosis.
false
Animal viruses always kill cells they infect.
false
In the lysogenic stage of phage replication, the host cell is lysed.
false
Once a phage becomes lysogenic, it will remain lysogenic and never be lytic again.
false
True or false: Viruses belong to the Domain Archaea
false
Viral nucleic acid is made inside the bacterium and is combined with viral protein coat already present outside.
false
Viruses can be grown on culture media like bacteria.
false
Helical capsid
have rod shaped capsomeres that bond together to form a series of hollow discs resembling a bracelet
Direct fusion
in this form of penetration, the envelope merges directly with the membrane
The activation of a prophage to enter the lytic cycle is called
induction
In vivo
lab bred animals and embryonic bird tissues are used to culture viruses
The viral capsid is
only around the nucleic acid and composed of proteins
In phage replication, _______.
only the phage nucleic acid enters the bacterial cell
Select the infectious agents that are noncellular.
satellite viruses, prions, viroids
Bacteriophage
"bacteria eating": Most contain double-stranded DNA, but some RNA types exist as well. Every bacterial species is parasitized by various specific bacteriophages. The bacteria they infect are often more pathogenic for humans
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
Prophage
A lysogenized bacteriophage; a phage that is latently incorporated into the host chromosome instead of undergoing viral replication and lysis.
Which drug targets can be found on both bacterial cells and viral particles?
None of the choices are possessed by viruses.
The capsid of a virus is
a protein shell that surrounds the nucleic acid
The general steps in viral replication (in order) are
adsorption, penetration, synthesis, assembly, release
Endocytosis
an entire virus is engulfed by the cell and enclosed in a vacuole or vesicle
Retroviruses
carry their own enzymes to create DNA out of their RNA
Latency
cell harbors the virus and is not immediately lysed: Can last from a few weeks to the remainder of the host's life
Inclusion bodies
compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasm
Loeffler and Frosch
discovered animal virus in cattle
Beijernick
discovered tobacco mosaic virus in plants
Every virus particle contains
either DNA or RNA
Viruses are viewed with
electron microscope
Syncytia
fusion of multiple damaged host cells into single large cells containing multiple nuclei (giant cells)
The polio vaccine currently used in the United States, the Salk vaccine, consists of polioviruses that have been treated with chemicals so that they can no longer reproduce within host cells and thus cannot establish an infection. They are referred to as _______, rather than dead, viruses.
inactive
Viruses are usually _________ in size, and their structure is best viewed through the use of ________ microscopy
nanometers; electron
Complex capsid
only found in the viruses which infect bacteria, they can take many shapes, and are never enveloped
A major difference in the replication of animal viruses and bacteriophages is the ______ step.
penetration
A viral infection in which the virus can remain latent in the host cell for weeks to years is described as a(n) _________ infection, and may lead to cancer if host DNA is altered.
persistent
An infection in animals similar to a lysogeny in bacteria is called a(n) ______ infection.
persistent
Viral capsids are composed of
protein
In the attachment step of phage replication, _______.
protein fibers in the phage tail attach to specific receptors on the bacterial cell wall
When present, what is the viral envelope composed of?
proteins and lipids
An envelope is acquired during which step of the viral life cycle?
release
In general, viruses are ________ than bacterial or protozoan pathogens and are most often measured in units called ________.
smaller; nanometers
In viral entry by endocytosis
the host cell's plasma membrane surrounds the whole virion and forms a vesicle
What will happen once a virus has entered a host cell and uncoated?
the synthesis of new virions will occur
Icosahedral Capsid
these capsids form an icosahedron, a 3d, 20 sided figure with 12 evenly spaced corners
A portion of the viral envelope comes from the cell membrane of the host cell.
true
Almost immediately upon entry, the viral nucleic acid alters the genetic expression of the host cell.
true
Both enveloped and naked viruses can enter a cell by endocytosis.
true
Both lytic and lysogenic cycles eventually lead to bacterial host cell damage.
true
RNA viruses
can be double-stranded, but more often single-stranded: can be positive sense or negative sense; Replicated and assembled in the cytoplasm