Deck 26: Poxviruses

Question 1

We no longer vaccinate people for smallpox because there are no stocks of smallpox anywhere on the planet.

Answer 1

False

Question 2

The gene regulation cascade of poxviruses is controlled by virus produced transcription factors.At what point in the virus replication cycle is the viral early transcription factor synthesized?

A)Early
B)Delayed Early
C)Intermediate
D)Late
E)All of the above.

Answer 2

D

Question 3

The mRNAs of poxviruses do not undergo splicing.Which of the following explains why?

A)Poxvirus genomes are small and they need to conserve genome space.
B)Poxviruses replicate in the cytoplasm of infected cells.
C)They do not need to regulate gene expression through alternative splicing.
D)They do not encode the proteins that carry out mRNA splicing.
E)Poxvirus mRNAs do not contain exons.

Answer 3

B

Question 4

Intermediate and late transcripts from poxviruses have a unique "poly(A)head" near the 5' end of the mRNA.What is the proposed function for this structure?

A)It binds to the poly(A)tails at the 3' end of the mRNA.
B)It stabilizes and protects the 5' end of the genome.
C)It aids in recognition of the AUG start codon by ribosomes.
D)It helps the nascent transcript bind to the viral RNA polymerase during transcription.
E)It associates with the cap binding complex.

Question 5

Which of the following describes the structure of the vaccinia virus genome?

A)Linear DNA with covalently closed ends.
B)Linear DNA with free ends.
C)Linear DNA with protein-bound ends.
D)Multiple linear DNA segments
E)Covalently closed circle of DNA.

Question 6

During infection with poxviruses,all of the following proteins are produced from early genes EXCEPT:

A)mRNA processing enzymes.
B)Viral Intermediate Transcription Factor.
C)Viral Early Transcription Factor.
D)Viral DNA-dependent DNA polymerase.
E)Viral DNA-dependent RNA polymerase.

Question 7

If viral DNA replication is inhibited in poxviruses,which of the following genes will not be expressed?

A)Gene encoding the mRNA processing enzymes.
B)Genes encoding virion structural proteins.
C)Genes encoding DNA replication enzymes.
D)Gene encoding the RNA polymerase subunits.
E)Genes encoding the nucleotide metabolism enzymes.

Question 8

Which of the following describes the major distinguishing feature of poxviruses when compared to other DNA containing viruses that replicate in eukaryotic cells?

A)They encode their own DNA polymerase.
B)They have large complex genomes that encode over 100 different proteins.
C)They have large complex virions.
D)They replicate exclusively in the cytoplasm of infected cells.
E)They encode a wide-variety of regulatory proteins.

Question 9

Which of the following cellular components is used to help extracellular virus particles of poxviruses reach and infect neighboring host cells?

A)Export vesicles.
B)Actin containing microvilli.
C)Microtubules.
D)Golgi-derived cisternae
E)Viroplasm.

Question 10

DNA replication in poxviruses uses a "rolling hairpin" model,similar to the method used by viruses in which of the following families?

A)Parvoviruses
B)Polyomaviruses
C)Adenoviruses
D)Herpesviruses
E)Baculoviruses

Question 11

For most of human existence,which of the following was the approximate fatality rate from smallpox infection in the countries where it was endemic?

A)1%
B)10%
C)25%
D)50%
E)100%

Question 12

Smallpox was named in 15^th century France to distinguish it from "large pox" or syphilis.

Question 13

Which of the following describes the process of variolation,which was an early method to prevent smallpox infections?

A)Exposure of children to milkmaids infected with cowpox.
B)Quarantine of smallpox victims for 40 days.
C)Use of plant extracts to prevent smallpox infection.
D)Blowing powdered pock scabs into the nose.
E)Exposure of young children to people with an active smallpox infection.

Question 14

Poxviruses produced two distinct types of virions.Which of the following describes the primary role of the extracellular virus particle?

A)They regulate the host cell antiviral defenses.
B)They are transmitted via an insect vector.
C)They infect new cells and tissues within a single host.
D)They are transmitted between hosts.
E)They can survive harsh environmental conditions.

Question 15

If a purified poxvirus genome was heated to melt the hydrogen bonds holding the two strands of DNA together,which of the following would describe the structure of the genome?

A)Multiple pieces of single-stranded DNA
B)Two linear pieces of single-stranded DNA
C)A covalently closed circle of double-stranded DNA.
D)Two single-strand circles entwined together.
E)A circle of single-stranded DNA.

Question 16

Which of the following groups of organisms are the primary hosts for poxviruses?

A)Humans
B)Insects
C)Plants
D)Plants and insects.
E)Birds,mammals and insects.

Question 17

Poxviruses express viral proteins that interfere with all of the following host-defense systems EXCEPT:

A)Interferon induced PKR kinase system.
B)Complement system.
C)Interleukin-1 cytokine activation.
D)Production of antibodies by B lymphocytes.
E)Tumor-necrosis factor activity.

Question 18

One of the strategies used by poxviruses to inhibit host defenses involves the synthesis of a viral serpin.What is the function of the serpin?

A)It inhibits components of the complement system.
B)It prevent the presentation of peptides on MHC-I.
C)It is a soluble receptor for the tumor necrosis factor.
D)It binds to the PKR kinase and inhibits its activity.
E)It inhibits a serine protease that activates interleukin-1 $\beta$ .

Question 19

Because poxviruses replicate exclusively in the cytoplasm of the host cell,they must encode which of the following enzymes?

A)DNA-dependent RNA polymerase.
B)DNA-dependent DNA polymerase.
C)mRNA processing enzymes.
D)Enzymes to produce deoxoynucleotides.
E)All of the above are encoded.

Question 20

Smallpox was eliminated from the human population through the use of antiviral drugs.

Question 21

Vaccinia virus virions do not need any host proteins to carry out transcription and processing of the early gene mRNAs.

Question 22

Describe the unique structure of the genome of poxviruses and how this genome is replicated to solve the problem with replicating the ends of linear DNA.

Question 23

Intermediate and late gene transcription of poxviruses does NOT require any host cell proteins.

Question 24

Vaccinia virus has been developed to express foreign proteins from bacteriophage T7 promoters.

Question 25

Describe the observations that Edward Jenner made and the experiment that he carried out to show that the "cowpox" virus could protect people from smallpox.