Quiz P3 Flashcards
The growth of viruses in a culture is described as a one-step growth curve, because
virion numbers show no increase during intracellular replication and can only be counted after the virions burst from the host cell.
assembly and release actually occur in one step.
there is only one step in the viral life cycle which leads to only one replicative cycle in a culture.
the eclipse phase prevents the plating and enumeration of virions although new virions are produced at a steady rate during the eclipse phase.
virion numbers show no increase during intracellular replication and can only be counted after the virions burst from the host cell.
When a virus enters a host cell in which it can replicate, the process is called a(n)
infection.
excision.
prophage.
insertion
infection
Viral replication occurs
Viral replication occurs
extracellularly.
intracellularly.
both intracellularly and extracellularly.
either intracellularly or extracellularly, depending on the virus involved.
intracellularly
Viruses have both an intracellular and an extracellular form.
Viruses have both an intracellular and an extracellular form.
True
False
T
Penetration requires that the entire virus is inserted within the host.
Penetration requires that the entire virus is inserted within the host.
True
False
F
Viruses can redirect host metabolic functions.
Viruses can redirect host metabolic functions.
True
False
T
lytic infection results in death of the host cell.
A lytic infection results in death of the host cell.
True
False
T
e concentration of infectious plaque forming units (pfu) per volume of fluid is known as the
The concentration of infectious plaque forming units (pfu) per volume of fluid is known as the
virulence.
titer.
infectivity.
fluid infectivity.
titer
The use of ________ is the easiest and most effective way of studying many animal and plant viruses.
The use of ________ is the easiest and most effective way of studying many animal and plant viruses.
prophages
live hosts
bacterial cultures
tissue or cell culture
tissue or cell culture
Viruses infecting ________ are typically the easiest to grow in the laboratory.
Viruses infecting ________ are typically the easiest to grow in the laboratory.
plants
fungi
animals
prokaryotes
prokaryotes
When solutions of host cells and infectious virions are mixed and spread on an agar plate, ________ form where viruses lyse the host cells.
When solutions of host cells and infectious virions are mixed and spread on an agar plate, ________ form where viruses lyse the host cells.
prophages
colonies
plaques
insertion sequences
plaques
Bacteriophage have a ________ complex structure than animal viruses, because ________.
Bacteriophage have a ________ complex structure than animal viruses, because ________.
more / the bacteriophage must penetrate the peptidoglycan cell wall
less / there prokaryotic cells have a simple structure compared to eukaryotic cells
more / bacteriophages must be coated by lipopolysaccharide to attach to bacterial cells
less / the bacteriophage does not have to penetrate the nucleus
more / the bacteriophage must penetrate the peptidoglycan cell wall
Virions infecting some bacteria possess the enzyme ________ that makes a small hole in the bacterial cell wall, allowing the viral nucleic acid to enter.
Virions infecting some bacteria possess the enzyme ________ that makes a small hole in the bacterial cell wall, allowing the viral nucleic acid to enter.
infectase
lysozyme
peptidoglycanase
nuclease
lysozyme
Cellular receptors may be composed of Cellular receptors may be composed of carbohydrates. lipids. proteins. combinations of proteins, carbohydrates, and/or lipids.
combinations of proteins, carbohydrates, and/or lipids.
T4 genes are transcribed by host RNA polymerase, yet the transcription of T4 genes is carefully controlled so that groups of T4 genes are transcribed at specific times after infection. How is this accomplished?
T4 genes are transcribed by host RNA polymerase, yet the transcription of T4 genes is carefully controlled so that groups of T4 genes are transcribed at specific times after infection. How is this accomplished?
Rolling circle replication of the viral genome ensures that the genes are available for transcription in the correct order.
Early and middle T4 genes encode for proteins that modify the activity of sigma factors and host RNA polymerase to regulate the expression of T4 genes.
Early T4 genes encode for proteolytic enzymes that destroy the host RNA polymerase. Subsequently a viral polymerase is created that transcribes the middle and late genes in the correct order.
Each group of T4 genes has a different promoter that indicates that order in which they should be transcribed in based on the affinity of the promoter for the host RNA polymerase.
Early and middle T4 genes encode for proteins that modify the activity of sigma factors and host RNA polymerase to regulate the expression of T4 genes
What would be the consequence of deleting the late T4 genes?
What would be the consequence of deleting the late T4 genes?
T4 capsid proteins would not be made.
T4 mRNA would not be produced.
ATP would not be produced and the T4 genome would not be packaged into the capsid.
The T4 genome would not be copied.
T4 capsid proteins would not be made.
Although T4 encodes over 250 proteins, it does not encode its own RNA polymerase.
Although T4 encodes over 250 proteins, it does not encode its own RNA polymerase.
True
False
T
The consequence of an infection by a temperate bacteriophage is that the bacterial cell
The consequence of an infection by a temperate bacteriophage is that the bacterial cell
may lyse before it divides or may continue to divide and replicate both the virus and the cell.
lyses before it gets a chance to divide.
never lyses but continues to divide and replicate both the virus and the cell.
divides faster at moderate temperatures.
may lyse before it divides or may continue to divide and replicate both the virus and the cell.
The virus repressor protein
The virus repressor protein
controls both the lytic genes on the prophage and prevents an incoming virus of the same type.
does not control the prophage’s lytic genes but does control the incoming genomes of the same virus.
controls the prophage’s lytic genes but not the incoming genomes of the same virus.
has different actions in different situations
controls both the lytic genes on the prophage and prevents an incoming virus of the same type.
Ch8 MC Q 13
deletion or inactivation of the cro gene
A virus that kills its host is said to be
A virus that kills its host is said to be
temperate.
virulent or lysogenic, but not temperate.
lysogenic.
lytic or virulent.
lytic or virulent.
Viruses can confer additional properties on their host cells, which can in turn be inherited.
Viruses can confer additional properties on their host cells, which can in turn be inherited.
True
False
T
Temperate viruses can enter into either a lytic or lysogenic cycle.
Temperate viruses can enter into either a lytic or lysogenic cycle.
True
False
T
How is penetration different in animal viruses as compared to bacterial viruses?
Hints
Hint 1.
[[viral penetration]] During the life cycle of any virus, once the virus has attached to the surface of the target cell, penetration must occur. Part of the viral particle or the entire particle must enter the target cell in order for viral replication to occur.
How is penetration different in animal viruses as compared to bacterial viruses?
The viral genome penetrates an animal cell, while the entire viral particle penetrates a bacterial cell.
There is no difference; only the viral genome penetrates both cell types.
The entire viral particle penetrates an animal cell, while only the viral genome penetrates a bacterial cell.
There is no difference; the entire viral particle penetrates both cell types.
The entire viral particle penetrates an animal cell, while only the viral genome penetrates a bacterial cell.
Differentiate between persistent and latent animal virus infections.
Hints
Hint 1.
[[animal virus infections]] Infection of an animal cell by a virus can lead to different results. Some viruses immediately replicate the virus and lead to viral release by cell destruction. Others keep the host cell alive for long periods of time while releasing new virus particles.
Differentiate between persistent and latent animal virus infections.
Persistent infections always lead to cell lysis, while latent infections never lead to cell lysis.
In a latent infection, the host cell is continually releasing new viral particles slowly. In a persistent infection, there are periods of time where the virus is not replicating and creating new viral particles.
In a persistent infection, the host cell is continually releasing new viral particles slowly. In a latent infection, there are periods of time where the virus is not replicating and creating new viral particles.
Persistent infections can cause transformation of the host cell, which can lead to the development of cancer. Latent infections do not cause transformation.
In a persistent infection, the host cell is continually releasing new viral particles slowly. In a latent infection, there are periods of time where the virus is not replicating and creating new viral particles.
Some viruses are associated with cancer. There are a variety of ways in which viruses may affect a cell in a way that may lead to cancer. Based on your knowledge of the life cycles of viruses and of molecular genetics, what is one way that this might happen?
Hints
Hint 1.
[[Molecular genetics of cancer]] Cancer develops when mutations occur that disrupt the normal regulation of the cell cycle. Based on what you know about the life cycles of viruses, how might a virus be associated with a mutation?
Some viruses are associated with cancer. There are a variety of ways in which viruses may affect a cell in a way that may lead to cancer. Based on your knowledge of the life cycles of viruses and of molecular genetics, what is one way that this might happen?
Viral genetic material inserts into a host genome, placing a promoter in a new location and turning on a gene that had previously been turned off.
Viral genetic material inserts into a host genome in a repetitive noncoding region.
Viral genetic material inserts into a host genome close to the termination sequence, far downstream of the promoter, and causes a silent mutation.
Viral genetic material inserts into a host genome and causes a mutation in a promoter, turning off a gene that had previously been turned on.
Viral genetic material inserts into a host genome, placing a promoter in a new location and turning on a gene that had previously been turned off.
Blocking polyomavirus SV40’s ability to integrate its genome into host cells would
Blocking polyomavirus SV40’s ability to integrate its genome into host cells would
increase the latent period of SV40.
increase the rate of transformation.
avoid cancer development from the virus.
switch SV40 into a lytic lifecycle which would be especially harmful to the host cells.
avoid cancer development from the virus.
Herpesviruses can cause all of the following diseases in humans EXCEPT
Herpesviruses can cause all of the following diseases in humans EXCEPT
chicken pox.
spongiform encephalopathy.
cancer.
cold sores.
spongiform encephalopathy.
Herpesviruses can cause \_\_\_\_\_\_\_\_\_\_. Hints Hint 1. [[Herpesviruses]] Herpesviruses are double-stranded DNA viruses that have an envelope surrounding the viral capsid. These viruses can remain latent in the human body for long periods of time. Herpesviruses can cause \_\_\_\_\_\_\_\_\_\_. cancer cold sores or fever blisters shingles All of the listed responses are correct.
All of the listed responses are correctTrue
Evolution is driven by Evolution is driven by random mutation. selection pressure applied to random mutation. novel metabolic pathways. selection pressure.
selection pressure applied to random mutation.
According to the RNA world hypothesis, which of the following was the correct sequence of developments?
Hints
Hint 1.
[[RNA world hypothesis]] The RNA world hypothesis is a hypothesis that has been proposed to help explain the sequence of events that led to the origin of cellular life.
According to the RNA world hypothesis, which of the following was the correct sequence of developments?
biological building blocks (e.g., amino acids, sugars, and nucleosides), then RNA (including catalytic and self-replicating RNA), then protein synthesis, then DNA, then lipid bilayers surrounding early cellular life
biological building blocks (e.g., amino acids, sugars, and nucleosides), then lipid bilayers surrounding these building blocks, then RNA (including catalytic and self-replicating RNA), then protein synthesis, then DNA
biological building blocks (e.g., amino acids, sugars, and nucleosides), then DNA, then RNA (including catalytic and self-replicating RNA), then protein synthesis, then lipid bilayers surrounding early cellular life
biological building blocks (e.g., amino acids, sugars, and nucleosides), then RNA (including catalytic and self-replicating RNA), then DNA, then protein synthesis, then lipid bilayers surrounding early cellular life
biological building blocks (e.g., amino acids, sugars, and nucleosides), then RNA (including catalytic and self-replicating RNA), then protein synthesis, then DNA, then lipid bilayers surrounding early cellular life
What was the LUCA?
Hints
Hint 1.
[[Terminology]] LUCA stands for Last Universal Common Ancestor.
What was the LUCA?
the last eukaryote before eukaryotes diversified
the type of prokaryote that evolved into a eukaryote
the last organism prior to the divergence of bacteria and archaea
the first cellular organism to evolve
the last organism prior to the divergence of bacteria and archaea
LUCA is
LUCA is
actually somewhat of a misnomer because it is now believed that each of the domains arose independently.
the individual ancestor of each of the three domains.
the last universal common ancestor.
All of the answers are correct.
the last universal common ancestor.
Compared with today, the temperature on Earth during its first half-billion years was probably
Compared with today, the temperature on Earth during its first half-billion years was probably
considerably colder.
about the same as today on average, but the diurnal fluctuations were much greater.
considerably warmer.
about the same as today.
considerably warmer.
Microorganisms were probably restricted to the oceans and subsurface environments until
Microorganisms were probably restricted to the oceans and subsurface environments until
the ozone layer was made.
phototrophy evolved.
chemoorganotrophy developed.
aquatic life brought them onto land.
the ozone layer was made.
The first catalytic and self-replication biological molecule was most likely
The first catalytic and self-replication biological molecule was most likely
proteins.
ATP.
RNA.
DNA.
RNA.
The earliest nucleic acid was probably a simple DNA molecule.
The earliest nucleic acid was probably a simple DNA molecule.
True
False
False
The establishment of DNA as the genome of the cell may have resulted from the need to store genetic information in a more stable form than RNA.
The establishment of DNA as the genome of the cell may have resulted from the need to store genetic information in a more stable form than RNA.
True
False
True
When exposed to UV light, oxygen gas produces ozone gas.
When exposed to UV light, oxygen gas produces ozone gas.
True
False
True
The earliest stromatolites were probably formed by
The earliest stromatolites were probably formed by
anoxygenic lithotrophs.
oxygenic lithotrophs.
oxygenic phototrophs.
anoxygenic phototrophs.
anoxygenic phototrophs.
Stromatolites are layered mounds, columns, and sheet-like sedimentary rocks. They were originally formed by the growth of layer upon layer of cyanobacteria, a single-celled photosynthesizing microbe that lives today in a wide range of environments ranging from the shallow shelf to lakes, rivers, and even soils.
If there were photosynthetic organisms present when the earth was primarily anoxic, why was the development of cyanobacteria critical for the oxidation of the atmosphere?
Hints
Hint 1.
[[early earth]] The biochemical processes that were carried out on the early earth were all anaerobic. There was little or no oxygen available. In addition, the temperatures were thought to be very hot.
If there were photosynthetic organisms present when the earth was primarily anoxic, why was the development of cyanobacteria critical for the oxidation of the atmosphere?
The early forms of photosynthesis did produce oxygen, but it was not enough to make a difference in the atmosphere.
The early forms of photosynthesis were carried out in the water and there was no way for the oxygen to move into the atmosphere.
The early forms of photosynthesis did not produce oxygen as a waste product.
Cyanobacteria carry out anoxic photosynthesis.
The early forms of photosynthesis did not produce oxygen as a waste product.
It is hypothesized that early photosynthesis was anoxygenic. If so, what was the effect of the appearance of organisms using oxygenic photosynthesis?
Hints
Hint 1.
[[Anoxygenic]] “Anoxygenic” means without generating oxygen.
It is hypothesized that early photosynthesis was anoxygenic. If so, what was the effect of the appearance of organisms using oxygenic photosynthesis?
The increase in organisms using oxygenic photosynthesis led to an increased ability to use solar radiation.
The increase in organisms using oxygenic photosynthesis led to a decrease in the diversity of organisms as they outcompeted organisms using anoxygenic photosynthesis.
Organisms using oxygenic photosynthesis release oxygen into the atmosphere, causing an increase in the oxygen in the atmosphere and allowing for the development of aerobes.
The increase in oxygen in the atmosphere from organisms using oxygenic photosynthesis caused a great decrease in diversity as obligate aerobes were killed.
Organisms using oxygenic photosynthesis release oxygen into the atmosphere, causing an increase in the oxygen in the atmosphere and allowing for the development of aerobes.
It is hypothesized that early photosynthesis was anoxygenic. Think about the role of oxygen in photosynthesis as carried out by green plants, green algae, and cyanobacteria (as opposed to modern organisms that use anoxygenic photosynthesis). What would have been different in anoxygenic photosynthesis (or is different in modern organisms that use anoxygenic photosynthesis)?
Hints
Hint 1.
[[Anoxygenic]] “Anoxygenic” means without generating oxygen.
It is hypothesized that early photosynthesis was anoxygenic. Think about the role of oxygen in photosynthesis as carried out by green plants, green algae, and cyanobacteria (as opposed to modern organisms that use anoxygenic photosynthesis). What would have been different in anoxygenic photosynthesis (or is different in modern organisms that use anoxygenic photosynthesis)?
Anoxygenic organisms would not have been able to produce ATP, only NADPH.
Anoxygenic organisms do not require light while oxygenic organisms do require light.
Anoxygenic organisms would have been able to produce only NADPH, not ATP.
Green plants, green algae, and cyanobacteria split H2O to replace an excited electron in noncyclic photophosphorylation. Oxygen is released into the atmosphere. In anoxygenic photosynthesis, a different molecule (such as H2S) is split and a different product (such as sulfur) is released.
Green plants, green algae, and cyanobacteria split H2O to replace an excited electron in noncyclic photophosphorylation. Oxygen is released into the atmosphere. In anoxygenic photosynthesis, a different molecule (such as H2S) is split and a different product (such as sulfur) is released.
It is believed that phototrophy arose approximately 3.3 billion years ago in
It is believed that phototrophy arose approximately 3.3 billion years ago in
LUCA.
Bacteria.
Archaea.
Eukarya.
Bacteria
As oxygen appeared in the atmosphere, ________ also accumulated, which formed a protective barrier that protects the Earth from ________.
As oxygen appeared in the atmosphere, ________ also accumulated, which formed a protective barrier that protects the Earth from ________.
sulfate / hydrogen sulfide
elemental sulfur / volcanism
ozone / UV radiation
ferrous iron / hydroxylating radicals
ozone / UV radiation
