Deck 11: Viral Molecular Biology

Question 1

A cell infected with a bacteriophage T4 mutant in tail fiber assembly will accumulate:

A) individual heads and tails
B) heads only
C) tails only
D) heads joined to tails
E) protein subunits for all components

Answer 1

D

Question 2

Hepatitis C virus belongs to the ___________ group.

A) orthomyxoviruses
B) togaviruses
C) flaviviruses
D) coronaviruses
E) filoviruses

Answer 2

C

Question 3

Which of the following best describes the genome of the influenza virus?

A) negative-strand segmented RNA
B) positive-strand segmented RNA
C) negative-strand single-piece RNA
D) positive-strand single-piece RNA
E) double-stranded RNA

Answer 3

A

Question 4

Drug resistance arises quickly for Hepatitis C virus due to:

A) high error rates of host RNA-dependent RNA polymerase
B) high error rates of viral DNA-dependent reverse transcriptase
C) higher error rates at the constant regions within the RNA genome
D) higher error rates at the hypervariable regions within the RNA genome
E) higher error rates at the regions encoding viral proteases

Question 5

Influenza shows cyclic appearance of extremely virulent strains that cause __________ with high mortality, such as that of 1918, which infected 20% of the world's population and killed more people than World War I.

A) mutation
B) arrestation
C) epidemic
D) pandemic
E) transgenic

Question 6

Which of the following is NOT a picornavirus?

A) poliovirus
B) coxsackievirus
C) influenza virus
D) rhinovirus
E) aphthovirus

Question 7

Mutations that allow viruses to replicate under one set of conditions but not under another set of conditions are known as __________ mutations.

A) suppressor
B) lethal
C) conditional lethal
D) silent
E) nonsense

Question 8

Once T4 DNA has been injected into host cells, all of the following virus life cycle stages take place EXCEPT:

A) The early genes are transcribed and translated to proteins, including DNase to cleave host DNA.
B) T4 undergo lytic or lysogenic cycles depending on environmental factors.
C) Late in the T4 life cycle, phage-encoded lysozymes lyse the host cell, releasing about 200 phage particles.
D) T4 DNA undergoes rolling-circle replication generating a multigenome concatemer for packaging into viral heads.
E) T4 capsid assembles automatically in a predetermined order from part encoded by phage genes.

Question 9

The term quasispecies describes which of the following?

A) within a single infected patient, the high mutation rates generate multiple virus strains with differing properties of replication, tissue tropism, and drug resistance
B) the infected patients within a single hospital, the high mutation rates generate multiple virus strains with differing properties of replication, tissue tropism, and drug resistance
C) the infected patients within a single community, the high mutation rates generate multiple virus strains with differing properties of replication, tissue tropism, and drug resistance
D) the infected patients within a single population, the high mutation rates generate multiple virus strains with differing properties of replication, tissue tropism, and drug resistance
E) genome recombination between virus and host genomes that contributes to genetic variability

Question 10

What is the function of the lysosome during replication cycle of heptatitis C virus (HCV)?

A) binding to host receptors
B) counteracting pathogenic microbes
C) triggering fusion between HCV viron and endoplasmic reticulum
D) cleaving to HCV polypeptide
E) triggering the virion envelope to fuse with the endosome membrane

Question 11

In HCV, the genome recombination takes place through a process known as:

A) reverse transcription
B) DNA switching
C) polypeptide elongation
D) exocytosis
E) template switching

Question 12

T4 DNA is synthesized by which of the following mechanisms?

A) Bidirectional replication
B) $\theta$ replication
C) Unidirectional replication
D) Rolling-circle replication
E) Okazaki semidissentious replication

Question 13

Which of the following statements does NOT describe the T4 infection?

A) Tail fibers of T4 contact the outer membrane.
B) The sheath contracts and the internal tube penetrates the outer membrane.
C) Only viral DNA is transferred into host cells.
D) T4 protein coats are absorbed into the host cells and degraded.
E) T4 utilizes host machineries for replication of viral genome and viral particles.

Question 14

Which is the most important nonstructural protein of hepatitis C virus that functions in a host cell during viral replication?

A) NS2
B) NS3
C) NS4A
D) NS5B
E) NS4B

Question 15

Which of the following mutants provides the best tools to decipher the genetic pathways of cells?

A) point mutation mutants
B) temperature-sensitive mutants
C) nonsense mutation mutants
D) suppressor ribosome mutants
E) RNA polymerase mutants

Question 16

The __________ separation of early genes and late genes is common to the replicative cycles of many phages as well as viruses of eukaryotes.

A) spatial
B) physical
C) temporal
D) genetic
E) lytic

Question 17

Phage T4 genes are translated using host cell __________ and viral __________.

A) polymerases; ribosomes
B) ribosomes; tRNA
C) tRNA; ribosomes
D) tRNA; polymerases
E) mRNA; tRNA

Question 18

Heptatitis C virus binds to all the mentioned receptors EXCEPT:

A) CD81
B) SR-B1
C) CD44
D) LDLR
E) claudin-1

Question 19

All of the following are facts about hepatitis C virus (HCV) EXCEPT:

A) HCV is a (+) strand RNA virus, which requires RNA-dependent RNA polymerases for viral genome replication.
B) Its RNA genome starts with a 5' internal ribosome entry site (IRES), which facilitates initiation of translation.
C) The HCV virion binds host receptors at or near a tight junction and becomes endocytosed.
D) Host ribosome translates (+) strand RNA to one polyprotein, which is then cleaved to individual HCV proteins in endoplasmic reticulum.
E) New HCV progenies are transferred exclusively through a tight junction to infect other host cells.

Question 20

Most virus particles produced from an influenza virus infection are:

A) defective
B) virulent
C) lytic
D) lysogenic
E) mutated

Question 21

Cyclophilin A is a host protein that:

A) acts as a coreceptor for HIV
B) facilitates HIV entry into the nucleus
C) is incorporated in the HIV envelope
D) inhibits HIV replication
E) cuts the polyprotein into subunits

Question 22

The influenza reassortment process is enhanced by a particular feature of the virus, namely the __________ genome.

A) linear
B) circular
C) double-stranded
D) single-stranded
E) segmented

Question 23

RNA synthesis of influenza virus is primed by 7-methylguanine fragments of host mRNA, obtained by the "__________" method.

A) telomerase
B) rolling-circle
C) endocytosis
D) exocytosis
E) cap-snatching

Question 24

Which antiviral agent is currently used to treat influenza infections targeting viral neuraminidase?

A) Tamiflu
B) Pleconaril
C) Zidovudine
D) Acyclovir
E) Vitravene

Question 25

Which was the first virus demonstrated to cause cancer?

A) human immunodeficiency virus
B) Rous sarcoma virus
C) herpes simplex virus
D) coxsackievirus
E) rhinovirus

Question 26

A fusion peptide is associated with which influenza virus protein?

A) hemagglutinin
B) neuraminidase
C) matrix
D) nuclear-packaging protein
E) cap-stealing protein

Question 27

The presence of which enzyme determines the kind of host that may be infected by influenza?

A) urease
B) helicase
C) protease
D) DNA polymerase
E) RNA polymerase

Question 28

Worldwide, HIV infects one in how many adults?

A) 20
B) 50
C) 100
D) 500
E) 1,000

Question 29

Glycosylation and packaging of the HIV Env proteins occur in the:

A) endoplasmic reticulum
B) nucleus
C) membrane
D) Golgi
E) cytoplasm

Question 30

Some people are resistant to HIV infection because they:

A) lack CD4 receptors on their macrophages
B) lack CCR5 receptors on their macrophages
C) lack macrophages
D) produce proteases that destroy HIV
E) all of the above

Question 31

HIV-infected cells can fuse with a neighboring cell, resulting in the formation of a giant multinucleate cell called a(n):

A) transgene
B) syncytium
C) oncogene
D) tumor
E) retroelement

Question 32

The pol open reading frame of HIV encodes:

A) reverse transcriptase
B) integrase
C) protease
D) all of the above
E) none of the above

Question 33

The double-stranded DNA copy of HIV:

A) enters the nucleus from the cytoplasm
B) is synthesized in the nucleus
C) encodes an integrase prior to integration
D) contains hydroxymethylcytosine
E) has RNase activity

Question 34

Flu pandemics are associated with reassortment of which virus genes?

A) hemagglutinin
B) neuraminidase
C) matrix
D) A and B
E) all of the above

Question 35

The RNA dimer packed in the HIV virion includes two host tRNA molecules hybridized so as to present a 3' OH for __________ synthesis of DNA.

A) increasing
B) preventing
C) priming
D) decreasing
E) terminating

Question 36

Integrated retrovirus genomes that have accumulated mutations and no longer can generate virions are known as __________ retroviruses.

A) lysogenic
B) temperate
C) virulent
D) exogenous
E) endogenous

Question 37

Which of the following is NOT an accessory protein found in HIV that regulates its cell cycle?

A) Nef
B) Vpu
C) Tat
D) Rev
E) Gag

Question 38

The __________ virus envelope proteins recognize the specific protein sequence of CD4 and CCR5 in order to attach and enter the host cell.

A) HIV
B) influenza
C) T4
D) M13
E) polio

Question 39

Which of the following primers for nucleic acid replication is linked to the appropriate virus?

A) M2 and poliovirus
B) host caps and poliovirus
C) VPg and influenza virus
D) virus tRNA and herpes virus
E) host tRNA and HIV

Question 40

AZT, a component in the drug mixture given to AIDS patients, is an inhibitor of:

A) exit of endocytosed viruses
B) endocytosis
C) viral assembly
D) reverse transcriptase
E) neuraminidase

Question 41

Why isn't there a cure or vaccine for AIDS yet?

Question 42

Describe how priming is different for mRNA synthesis or template synthesis for viral progeny of influenza A virus.

Question 43

Why is hepatocyte tissue culture routinely used to understand the infection mechanism of hepatitis C virus (HCV)?

Question 44

Which type of virus has been used experimentally to transfer genes to Alzheimer's patients to promote nerve regeneration?

A) lentivirus
B) adenovirus
C) poliovirus
D) influenza virus
E) T4

Question 45

Approximately 60%-80% of Americans acquire herpes simplex, usually HSV-1, in epithelial lesions commonly known as:

A) chancres
B) pox
C) cold sores
D) shingles
E) hives

Question 46

What is a conditional lethal mutant? Give examples of two classes of conditional lethal mutants produced in T4 to demonstrate its assembly.

Question 47

What is meant by early and late genes of phage T4? What do they encode?

Question 48

Why do highly virulent strains of the influenza virus appear periodically?

Question 49

During latent herpes virus infections:

A) the virus produces early proteins but not late proteins
B) a latency-associated transcript is produced
C) no viral transcription occurs
D) virus DNA is integrated into host DNA
E) cell transcription machinery is silenced

Question 50

Why are capsids of icosahedral symmetry so common among viruses?

Question 51

Herpes simplex virus 1 replication involves:

A) viral DNA polymerase
B) rolling-circle replication
C) concatemer formation
D) all of the above
E) none of the above

Question 52

The segmented genome of influenza virus makes virus assembly problematic. How does the assembly mechanism package exactly eight segments correctly?

Question 53

The cell membrane releases mature HSV-1 virions through:

A) endocytosis
B) exocytosis
C) lysis
D) budding
E) slow release

Question 54

How does hepatitis C virus (HCV) gain entry into the host cell by utilizing "tight junctions"?

Question 55

Which of the following are NOT ways that viral vectors are modified to be made safer?

A) deleting virulence genes
B) avoiding genome insertion next to oncogenes
C) altering tissue specificity
D) using viruses that will trigger an immune response
E) avoiding germ-line infection

Question 56

Why is it difficult to visualize the hepatitis C virus (HCV), even by transmission electron microscopy (TEM) and scanning electron microscopy (SEM)?

Question 57

Herpes simplex virus and varicella-zoster virus cause primary __________ infections.

A) muscle
B) brain
C) neuron
D) epithelial
E) bone

Question 58

Herpes simplex virus 1 capsids receive envelope proteins from:

A) the cytoplasm
B) the nuclear membrane
C) the endoplasmic reticulum (ER)
D) either the nuclear membrane or the ER
E) the Golgi

Question 59

The causative agent of chickenpox is:

A) herpes simplex virus 1
B) herpes simplex virus 2
C) varicella-zoster virus
D) Epstein-Barr virus
E) HIV

Question 60

Viruses which specifically infect and lyse tumor cells are:

A) transfer vectors
B) temperate
C) lytic
D) lysogenic
E) oncolytic

Question 61

How are viruses used in gene therapy? What characteristics are important in viral vectors?

Question 62

What is the role of the variable and constant domains of the spike proteins in HIV infection?

Question 63

How can viruses be used to treat cancer? What are some features the viruses must have to be used in cancer therapy?

Question 64

What are some of the safety concerns involving viral vectors? Describe some of the safety features of viral vectors.

Question 65

Describe the replication cycle of HIV.

Question 66

What are the different types of retroelements and why do they exist within the human genome?

Question 67

Explain what happens in individuals infected with HIV who are homozygous for CCR5, heterozygous for a CCR5 deletion, or homozygous for a CCR5 deletion.

Question 68

Describe retroelements that are found in the human genome. How do endogenous retroviruses and retrotransposons differ?

Question 69

Describe the structure of herpes simplex virus. How is the attachment process of herpes simplex virus different from that of poliovirus and HIV virus?

Question 70

What types of infections are caused by herpes viruses? Describe the two possible types of replication cycles that occur with the herpes viruses.