Chapter 13
The genome of which of the following types of animal virus can act directly as mRNA?
+ssRNA
bacterial DNA degraded.
synthesis
Why is lysogeny advantageous to a bacteriophage?
the genetic material of the bacteriophage can be passed on to future generations of cells
Which of the following describes why viruses are not considered to be alive?
they lack cellular structure They cannot grow or respond to th the environment. Cannot reproduce on their own.
How are prions different from all other known infectious agents?
they lack nucleic acid
After a virus has invaded a cell, it takes control of the cell's metabolic machinery to produce more virions.
true
Animal viruses that are released by budding acquire a portion of the host cell membrane which becomes the viral envelope.
true
Human viruses can be difficult to treat because treatment might disrupt healthy cells also.
true
Oncogenes (genes that code for uncontrolled cell division) are genes that can cause cancer to develop. Viruses can carry copies of oncogenes in their genome and insert these genes into the host cell to cause cancer.
true
Replication of bacteriophages (viruses that attack bacteria) is described as either lytic or Lysogenic. The main difference in the two types of replication is in lysogenic replication the viral genomic material is inserted into the bacterial chromosome.
true
The HIV virus can become latent by using the enzyme reverse transcriptase to make a DNA copy of its +RNA genome that is then incorporated into hosts DNA.
true
The process by which a lysogenic phage is excised from the bacterial chromosome is called induction and can be started by ultraviolet light.
true
Viruses are primarily classified according to their
type of nucleic acid
Which of the following statements best describes a prion.
contains beta sheets and is a proteinaceous infectious agent
Which of the following describes why the chicken egg is used to grow human viruses.
inexpensive, largest of cells, sterile, and contain a nourishing yolk
This vrial nucleic acid can act directly as mRNA.
positive strand ssRNA
Double-stranded RNA genomes can be found
only in viruses
Which of the following types of animal virus requires RNA-dependent RNA transcriptase to be replicated?
-ssRNA
persistent viral infections
A virus that buds from a cell may allow the cell to remain intact for some time and The virses are slowly shed from the host cell.
which of the following is(are) correct about the lysogenic phage replication cycle?
Phage does not immediately take over the invaded cell. An inactive phage is called a prophage. The genome of the phage becomes part of the bacterial chromsome and is passed on to daughter cells.
In contrast to most dsDNA animal viruses, the poxviruses replicate solely in the cytoplasm of the host cell. This fact implies that the viral genome may encode
a DNA polymerase
During the intracellular state, a virus exists as
a nucleic acid
Viruses are shed slowly and steadily during
a persistent infection
Which of the following is not a difference between a bacteriophage and a virus that attacks animals?
animal viruses require chemical attraction to the hosts cell
A random process requiring little or no enzymatic activity.
assembly
Phages are nonmotile and make contact with host by random colliaion.
attachment
Which of the following events occurs in the lytic cycle of bacteriophage T4 infection but not in the lysogenic cycle?
digestion of host DNA
TheThe polio virus injects the viral genome into the animal cell.
direct penetration
Properties of viruses
do not divide or grow, not free living, acellular, replicate by using the host enzymes and organelles, and are obligate intracellular parasites
Replication takes place in the same manner that the hosts DNA is replicated
dsDNA
This type of virus causes most cases of diarrehea in infants.
dsRNA
Viruses can have genomes made up of nucleic acids which are not present in the genome of any cell. Which of the following types of nucleic acids are almost never found in cells?
dsRNA and ssDNA
The Adenoviruses and herpeviruses stimulate the cell to engulf the entire virus.
endocytosis
T4 uses lysozyme carried within the capsid to weaken petidoglycan cell wall.
entry
Which of the following would NOT be found as a component of a bacteriophage?
envelope
Lysogenic phages can change a pathogenic form of a bacterium into a harmless form.
false
Naked viruses always lyse the cell when being released.
false
The time of replication in both animal viruses and bacterial viruses is about 24 hours.
false
Viroids are small proteins that infect plants.
false
viruses come in many shapes and sizes they all have capsids made up of proteinaceous subunits and they all have a viral envelope that is acquired from the host cell.
false
Virus replication results in the death of the cell in a(n) __________ infection.
lytic
Measles and AIDs viruses fuse their membrane envelope with host cell membrane dump the capsid into host cell.
membrane fusion
This type of nucleic acid is not recognized by ribsomes so has to be converted.
negative sense ssRNA
The outermost layer of a virion fulfills which of the following functions of the virus?
protection and recognition
Which of the following is associated with the attachment of a bacteriophage to a bacterial cell?
random collisions, chemical attractions, and receptor specificity
Lysozyme completes work on cell walla and bacterium disintegrates.
release
Reverse transcriptase is associated with which of the following?
retroviruses
This type of virus uses reverse transcritase to make a DNA strand.
retroviruses
Before transcription takes place the host uses the viral nucleic acid as a templete to make a complementary strand of the viral nucleic acid.
ssDNA