VBS 2032: CH 13 LearnSmart
Bacteriophages play a fundamental role in which type of horizontal gene transfer?
Transduction
Which of the following best describes viruses?
Infectious agents
Which of the following directs the incorporation of phage DNA into a bacterial chromosome?
Integrase
Which of the following about classifying viruses is FALSE?
It is not as important as classifying organisms since they are not living entities
When two different strains of a segmented virus enter the same cell, reassortment of the gene segments can occur, resulting in _______
antigentic shift
Duration the _________ or maturation step in viral multiplication, capsids and genetic material are packaged into virions.
assembly
The image shows the ______ stage of the lytic cycle of the T4 phage.
assembly
Which of the following describes a consequence of lysogeny that could result in human disease?
Lysogenic conversion
Productive infection
New viral particles are produced
Reverse transcriptase is a(n) _____ polymerase
RNA-dependent DNA
Which of the following are viral protein components that attach to specific receptors on host cells?
Spikes and tail fibers
List the steps of an animal virus infection cycle in the correct order
1. Attachment 2. Penetration and uncoating 3. Synthesis of viral proteins and replication of the genome 4. Assembly 5. Release
Rank the following by size, from the smallest to largest, starting with the smallest at the top
1. Viruses 2. Bacteria 3. Human cells
Which of the two major categories of viral infections?
- Acute - Persistent
Replication of termperate phaves and lytic phages have which steps in common?
- Biosynthesis of viral components - Genome entry - Release - Attachment - Assembly
What are the two types of transduction?
- Generalized - Specialized
Viruses that infect bacteria are called
- Phages - Bacteriophages
Specialized transduction
- Results from errors in excision of the prophage - Transfers phage DNA and adjacent host genes - Produces defective phage particles
The study of viruses is important because
- Viruses can be a vehicle for horizontal gene transfer in bacteria - There are many medically important viruses that cause disease - Bactriophages play a significant ecological role in reducing bacterial populations in nature
In a lysogenized bacterium, __________ of the prophage results in a lytic infection
excision
This image shows the _______ stage of the T4 phage lytic cycle
genome entry
The molecules that viral spikes attach to on the host cell in order to gain entry are typically:
glycoproteins
All of the following are required for synthesis of new virus particles in a host cell EXCEPT
homologous recombination
Lysogeny is best described as
intergration of the viral genome into the host chromosome
(-) strand genome
is the complement to mRNA
Some pathogenic bacteria produce toxins that are encoded on prophage DNA, and these are examples of ______ conversion
lysogenic
In enveloped viruses, sandwiched between the nucleocapsid and the envelope is the
matrix protein
One of the early proteins expressed in the T4 lytic cycle is an enzyme called a _________ that degrades the bacterial DNA
nuclease
Most animal DNA viruses will replicate within the host cell's
nucleus
Apoptosis
programmed cell death, a process some non-enveloped viruses trigger as a means of release
The virally encoded polymerase needed for replication of RNA viruses is called a
replicase
HIV is described as a ________ because it uses reverse transcriptase to make a DNA copy from its RNA genome
retrovirus
An enzyme that uses an RNA molecule as a template to make a complementary copy of DNA is called
reverse transcriptase
(+) strand genome
serves as mRNA
Viral proteins that stick out from the viral envelop or capsid and attach to host cell receptors are termed
spikes
Phage DNA and proteins are made during the _____ stage of T4 lytic cycle
synthesis
Phage heads that contain only bacteria DNA are called generalized _________ particles
transducing
After a virus enters a cell, the nucleic acid separates from the protein coat, a process called
uncoating
lysis
used to describe the rupture or bursting of a cell
Regarding animal viruses, which of the following statements are true?
- Blocking a host receptor with a drug would prevent a virus from infecting that cell - Some viruses require more than one host receptor for attachment - Viruses use their spikes to attach to host cell receptors
Which of the following are diseases caused by prions?
- Bovine spongiform encephalopathy - Scrapie - Creutzfeldt-Jakob disease
Identify all the methods by which an enveloped virus can gain entry into animal cells
- Fusion of the viral envelope and the cell membrane - Endocytosis of the virus by the host cell
Which of the following occur during the synthesis stage of the T4 lytic cycle?
- Synthesis of phage DNA - Degradation of bacterial DNA - Synthesis of phage proteins
The hepatitis B virus sometimes causes an infection that results in a continuous and low-level production of virus particles. This type of infection pattern is specifically described as a(n) _________ viral infection
chronic
Infection of bacteria by ______ phages always end with the lysis of the host cell
lytic
Virus infections that result in the formation of new virus particles are described as
productive
Consequences of lysogeny include
- Immunity to superinfection - Lysogenic conversion
Which of the following are classified as persistent infection?
- Latent infections - Chronic infections
A viral infection in which the viral genome is integrated into an animal host cell chromosomes, yet can reactive to cause a productive infections, is categorized as a(n) _______ infection
latent
proofreading
RNA viruses have a higher mutation rate than DNA viruses because replicase lacks ______ ability
Replicases are _______ polymerases
RNA-dependent RNA
______ transduction is the result of excision error made as temperate phages transition from a lysogenic to a lytic cycle
Specialized
The accumulation of mutations in genes that encode viral surface proteins recognized by the immune system results in a type of antigenic variation called
Antigenic drift
Which of the following describes the various viral parts coming together to produce virions?
Assembly
This image shows the ______ stage of the T4 phage lytic cycle.
Attachment
Which types of viruses are released by budding?
Enveloped viruses
Which form of transduction results from excision errors during the transition from a lysogenic to lytic cycle?
Specialized
False
T or F: Enveloped viruses enter the host cell by endocytosis only, while non-enveloped viruses can enter host cell by fusion or endocytosis
False
T or F: Lysogens are more susceptible to reinfection by the same type of phage
False
T or F: Most bacteria engulf bacteriophages as part of the phage replication strategy
True
T or F: Viruses can contained either DNA or RNA, but not both
release
The stage of viral multiplication at which budding occurs is _____.
Latent state
Viral genome remains silent within the cell
Which is most important for attachment of a virus to a host cell?
Viral specificity for host receptors
A single virus particle is referred to as a
Virion
Which of the following statements about virus nucleic acid is true?
Viruses contain either DNA or RNA
Temperate; lytic
_____ phages have the option of entering the prophage state, while _____ phage always burst the host cell shortly after infection
A prion is best described as
a proteinaceous infectious agent
Infections that have a sudden onset of symptoms of relatively short duration are described as _______ infections
acute
The number of phage particles released from a host cell is called the _____ size
burst
A _____ is an infectious agent that lacks a capsid and consists only of RNA
viroid
Viruses are challenging to study because
- They can only be seen using an electron microscope - They are obligate intracellular parasites
Specialized transduction
- Transfers phage DNA and adjacent host genes - Results from errors in excision of the prophage - Produces defective phage particles
Which of the following processes are required for production of virus particles in a host cell?
- Translation of viral genes - Replication of viral genome - Transcription of viral genes
Which of the following are non-cellular infectious agents?
- Viroids - Prions - Viruses
Double-stranded genome
Consists of both a (+) and (-) strand
Reassortment of gene segments that encode viral surface proteins that are recognized by the immune system can result in a loss of the immune system's ability to recognize and respond to the virus. This phenomenon is called antigenic _______.
shift
Many animals viruses have proteins called ________ that attach to receptors on host cells
spike
Late proteins of the T4 lytic cycle include
- T4 tail fibers - T4 capsomere components
Which facts best support the position that viruses are not living organisms?
- Viruses are inert outside of a host - Viruses cannot reproduce on their own
Which of the following statements about viruses are true?
- Viruses contain RNA or DNA but not both - The viral capsid is compsed or protein
Which statements regarding viruses are true?
- Viruses that infect bacteria can be called phages - Viruses that infect bacteria can be called bacteriophages
Enveloped viruses can derive their envelopes from
- certain host organelles - the host cytoplasmic membrane
In order to infect an animal cell, viruses must
attach to receptors on the host cytoplasmic membrane
The binding of a bacteriophage surface protein to a host cell receptors is called
attachment
How does bacteriophage nucleic acid enter the host cell?
injection
Which of the following are non-cellular infectious agent?
- Viruses - Viroids - Prions
A ______ phage can either cause a lytic infection or can incorporate its DNA into the host genome as a prophage
Temperate
________ is a change in the phenotype of a lysogen as a consequence of the specific prophage it carries
lysogenic conversion