BIO Ch 26 Viruses
Of the following list, choose all that may be found in a viral particle.
A protein shell RNA An envelope DNA
Which protein would be most likely to have the potential to become a prion?
A protein that has two possible stable structures
In the _________ classification of viruses, 7 groups of viruses and every known virus can be placed in only one such group based on the way it duplicates/copies its genome.
Baltimore
How do viruses replicate?
Host cells' transcription and translation systems are used to replicate the genome and create capsid proteins.
Which of the following are the two types of structure typical of most viral capsids?
Icosahedral or helical
Can a virus be killed?
No, viruses are non-living and cannot die
Acquired immune deficiency syndrome is caused by a decline of ____________ cells.
T-helper
Which of the following is a virus with an icosahedral head, a capsid that contains primarily three proteins, a connecting neck with a collar and long whiskers, a long tail and a complex base plate?
T4 bacteriophage Correct
How does an enveloped virus recognize a suitable host cell?
The virus recognizes cell surface receptors that are embedded in the host's plasma membrane. Correct
If the reverse transcriptase enzyme carried by a retrovirus was mutated and nonfunctional, how would the virus be affected?
The virus would not be able to produce DNA to incorporate into the host's genome. Correct
How do prions "reproduce"?
They reproduce by converting healthy proteins into infectious prions
A harmless PrP is converted into the infective PrP
by an abnormal PrP which binds to the normal protein and causes it to become misfolded.
What is another way to describe the process by which an enveloped virus is released by the host cell?
exocytosis
HIV infects cells by recognizing the cell-surface markers with its own
glycoprotein
In viral entry by endocytosis
host plasma membrane surrounds whole virion and forms a vesicle
The number of species and cell types that a virus can infect comprise its ______.
host range
The enormous genetic diversity of HIV has made it especially difficult to create a vaccine against the virus. We can attribute this genetic diversity to
the high error rate of reverse transcriptase.
How can the genetic information of retroviruses be characterized?
two copies of single-stranded RNA Correct
Select all TRUE statements concerning HIV/AIDS.
-AIDS kills the patient indirectly, as a result of opportunistic infections. -During latency, the viral genome is integrated in the chromosomes of macrophages and T cells. -Some AIDS drugs target the reverse transcriptase enyme.
Check all of the correct statements below that we have learned from using metagenomics as a tool to better understand viral ecology.
-In one liter of coastal water there are 10 times more viruses than bacteria In one liter of coastal water there are 10 times more viruses than bacteria Correct -Since only a small fraction of viruses cause disease in animals and plants, it is hard to isolate virsues. Since only a small fraction of viruses cause disease in animals and plants, it is hard to isolate virsues. Correct -Soil and water are good sources to analyze for virus metagenomics. Soil and water are good sources to analyze for virus metagenomics. Correct
All of the following are part of phage conversion
-expression of phage gene by host. -transcription and translation of phage gene. -integration of phage gene to form a prophage. -injection of phage gene into host.
Which of the following describes a virus?
A small biological particle comprised of nucleic acid enclosed in a protein coat obligate intracellular parasites 20-250 nm in diameter
Which example best represents one origin of emerging viral diseases?
A virus passes from pigs to humans. Correct
Why is it difficult to classify influenza viruses based on their host?
Because there are four types of influenza viruses that can infect many different hosts (humans, birds, pigs, dogs, cats)
What is the best reason why people must be vaccinated once a year for influenza?
Changing viral H-molecule regions. Correct
Which disease requires both a bacterium and a virus be involved?
Cholera - A bacterium infects the patient, but it only causes disease if a virus provided the toxin gene by phage conversion.
How is an enveloped virus structurally different from a phage, like T4?
Enveloped virus possess an additional membrane around their protein capsid, phage do not possess a membrane. Correct
An experimental chemical has been shown to selectively cleave phosphodiester bonds. How would this affect a virus?
Fragment the genome Correct
From what genome does the information come that produces an enveloped virus?
From both the host cell and the viral genome Correct
Which of the following statements about the types and subtypes of the influenza (flu) virus is FALSE?
Genetic recombination between influenza and other types of viruses is common. (True: -Flu subtype is determined by the kinds of proteins representing the H and N protein spikes making up the capsid of the virus. -High mutation rates create more diversity in strains of flu than does genetic recombination. -Of the three major types of flu virus (A, B, and C), only Type A can occur in humans, other mammals, and birds. -The A(H2N2) and the A(H3N2) strains of the virus require different vaccines.)
Gardasil is marketed as a cervical cancer vaccine, but it is actually a human papilloma virus (HPV) vaccine. Why is this done?
HPV in the cervical epithelial cells may cause the cells to become cancerous.
Integrase inhibitors work by:
Preventing the incorporation of the viral DNA into the genome
The HIV virus contains ____________ in its genome.
RNA
Other than the presence of RNA vs. DNA, how is a retrovirus different from other viruses?
Retrovirus carry an enzyme within the virion. Correct
Diseases such as scrapie in sheep, "mad cow" disease in cattle, and Creutzfeldt-Jakob disease in humans are known as
TSEs (transmissible spongiform encephalopathies).
This animation ends with a virus entering a host cell and its protein capsid degrading and releasing nucleic acid into the cell. What will occur next if this virus exhibits a lysogenic life cycle?
The viral DNA will be incorporated into the host's DNA. Correct
A mutation in the gene encoding the integrase enzyme renders the protein non-functional. How would this affect-the HIV infection cycle?
The viral DNA would not be able to integrate the viral genome into a chromosome.
Which statement best explains how HIV compromises the body's immune system?
They disable T-helper cells.
Which of the following statements best describes viral genomes?
They may be circular or linear, single-stranded or double-stranded, and composed of DNA or RNA.
Which of the following statements most accurately describes the host specificity of viruses?
Viruses infect all types of organisms, but individual viruses are very limited in the species and cell types they can infect.
Viruses are unable to reproduce without which of the following?
a host cell
Lysogenic Cycle
a viral reproductive cycle in which the viral DNA is added to the host cell's DNA and is copied along with the host cell's DNA prophage temperate viruses cell division replication viral genome repressed
Lyctic Cycle
a virus enters a cell, makes copies of itself, then causes the cell to explode replicated by viral assemply viral genome active virulent assembly step
How is the protein structure changed when a normal protein (PrPc) is changed into an infectious protein (PrPsc)?
an abnormal conformation is adopted arising from misfolding changed into another structure Correct
Viral spikes
attach specifically to host cell receptors
Phages are viruses that can infect
bacteria
The normal prion protein is
bound to the cell membrane of neurons.
Enveloped viruses are usually released from the host cell by
budding
HIV viruses exit the host cell using a process called ____________ .
budding
Replication of the HIV virus requires the production of ____________ using reverse transcriptase.
cDNA
The provirus state exists when
double-stranded viral DNA is integrated into host cell chromosome.
A layer of lipoprotein and glycoprotein that covers the outer surface of some viruses is the
envelope
A viral capsid with an overall ______ structure has a rodlike or threadlike appearance.
helical
Prions are
infectious proteins with no associated nucleic acid.
If a virus enters the lytic phase in a host's cell, it will cause the host cell to
lyse due to the action of enzymes. Correct
Which of the following diseases is(are) caused by prions?
mad cow disease and Creutzfeldt-Jacob disease in humans Correct
If the viral gene is AUGCCCAGG and the mRNA used to make the viral protein is UACGGGUCC, then the virus is a :
negative strand RNA virus
If the DNA of the provirus is transcribed
one long polygenic mRNA is produced.
HIV belongs to a category of virus called a ____________ .
retrovirus
Viruses that become established as stable parts of the host cell genome are called
temperate
After the virus nucleocapsid is released from the vesicle into the host cell cytoplasm
the capsid protein is removed. Correct
A scientist is studying the lysogenic cycle of the lambda 1 phage of Escherichia coli. This means that she is investigating
the integration and stabilizing of the lambda 1 phase into a host cell's genome. Correct
Scientists have demonstrated that the cholera bacteria, Vibrio cholerae, can exist as a rather harmless form or, by phage conversion, can exist as a disease-causing, virulent form. This conversion is caused by
the phage introducing a gene into the bacterium's chromosome that codes for the cholera toxin that can cause death in humans. Correct
The viral envelope contains some components that are from the host cell's genome and some from the viral genome
true
Mechanism for Releasing Enveloped Viruses The first event to occur is
viral spike proteins are inserted into host cell membrane. Correct
