Optional exam micro (study for final)
In a temperate infection the phage DNA becomes ______ into the host cell's chromosome; at this point the phage is called a ______.
b. integrated, prophage
Viruses were first identified:
because they caused an infection and were small enough to pass through filters that trapped bacteria.
Viruses may not be cultivated in
blood agar
viruses:
cannot independently perform metabolic activities.
The protein coat of a virus is called the:
capsid
The shape of the virus is determined by its
capsid
Once integrated, phage DNA can remain in the prophage state as long as
certain phage genes are repressed.
A virion is a(n)
complete, extracellular virus particle.
The bacterium that causes botulism disease is harmless until it:
contains a certain prophage DNA.
Outside of living cells, viruses are
d. metabolically inert.
A symptom of a transmissible spongiform encephalopathy (TSE) is:
degeneration of the brain and central nervous system.
Virulent (lytic) phages:
destroy bacteria
Temperate viruses:
do not always destroy their host.
Human viruses can enter human cells by fusion with the cell membrane or by:
endocytosis.
The viral envelope closely resembles the
eukaryotic cell membrane.
An exit method used by viruses which does not immediately destroy the host bacterium is
extrusion
The bacterial viruses that are released by a process termed extrusion are called
filamentous phages.
Influenza vaccines must be changed yearly because the amino acid sequence of the viral proteins change gradually over time. Based on this information, which is the most logical conclusion? The influenza virus
has an RNA genome.
Retroviruses differ from other RNA viruses by:
having reverse transcriptase instead of RNA-dependent RNA polymerase.
The integration of phage DNA into the bacterial chromosome occurs because of
identical DNA sequences in both.
a prophage:
is phage DNA that is integrated into bacterial DNA.
Resistance of some animals to certain viral diseases is based on
lack of specific receptors on the host cell.
Lysozyme is needed for some viruses to escape from the host cell. A virus that makes lysozyme will likely make it _______ in the infection cycle and will be ________.
late, lytic
In the region of budding, the inside of the plasma membrane becomes coated with
matrix proteins
Prions affect the
nervous system
Filamentous phage
only infect E. coli that have pili
Viral proteins can damage host cells by:
overwhelming the host cell with a large number of viruses.
Viruses that attack bacteria are called:
phages
Viral infections in humans spread via the circulatory system. Viral infections in plants spread from cell to cell via:
plasmodesmata.
Mad cow disease is an example of an infection caused by a
prion
The specificity of viruses to different types of cells is due to __________ sites on the host cell.
receptor
During phage replication, early proteins are produced. Early proteins are
regulatory proteins encoded by phage DNA.
The five stages of a lytic infection are attachment, penetration, __
replication
The protein projections on the surface of a virus that are involved in attachment to the host cell are called
spikes
Viroids characteristically are composed of
ssRNA
Viroids cause a variety of plant diseases and are composed only of:
strands of RNA.
In the replication of phage containing positive-sense DNA,
the host's enzymes are used to make dsDNA
What part of the attached bacteriophage enters through the host cell wall?
the nucleic acid.
The host range of a phage refers to
the number of different species of bacteria that the phage can infect.
Specialized transduction refers to which of the following?
the transfer of only a few specific genes from one bacterium to another
A phage that replicates inside the host cell and then lyses its host during its release is a
virulent or lytic phage.
Acute infections of animals 1. are a result of productive infection. 2. generally lead to long-lasting immunity. 3. result from integration of viral nucleic acid into the host. 4. are usually followed by chronic infectins. 5. often lead to tumor formation.
1,2
All phages must have the ability to 1. have their nucleic acid enter the host cell. 2. kill the host cell. 3. multiply in the absence of living bacteria. 4. lyse the host cell. 5. have their nucleic acid replicate in the host cell.
1,5
Which is a filamentous phage
M13
A restriction endonuclease is an enzyme that recognizes
a distinct base sequence in DNA and cleaves the DNA at that sequence.
Self-assembly refers to
a process in which viral protein components come together without enzyme facilitation.
The nucleic acid of a mature virion can take on several different forms, including a. linear or circular DNA. b. single- or double-stranded RNA c. single- or double-stranded DNA. d. All of these choices are correct.
all of these are correct
Phages are being considered for:
antibiotics in bacterial infections.
The correct order for the stages of a phage infection is:
attachment, penetration, transcription, replication of nucleic acid and protein, assembly, release
Bacteriophages are harmful to humans if they
attack helpful intestinal bacteria.
The burst size of the T4 phage is about 200 virions per cell. If the replicative cycle of T4 is 30 minutes, how many virions will be present after four hours of infection, assuming there is an unlimited number of host cells present to perpetuate the infection process?
2.56 virions x 1020
Place the following phage replication events in order of occurance: 1. penetration, 2. transcription, 3. attachment, 4. release, 5. assembly, 6. DNA and protein synthesis
3, 1, 2, 6, 5, 4
ssRNA bacteriophages such as MS2 must code for which enzyme in order to replicate?
RNA dependent RNA polymerase
A drug that interferes with viral self-assembly would be least effective on the spread of these types of viruses:
Temperate lysogenic prophage
Viruses exhibit several different strategies while in the host cell. Which of the following is NOT one of those strategies?
The virus takes over the host cell metabolism but does not replicate
