Question 1

Which of the following may explain why mimiviruses encode a high number of DNA repair enzymes?

Accepted Answer

A)  Their host produces a large number of nucleases.
B)  The method used to replicate the viral genome introduces many mutations.
C)  During long periods between infections,they are exposed to UV light.
D)  During entry,the genome would be exposed to oxidizing conditions.
E)  Both "c" and "d" are correct.

Question 2

The famous white cliffs of Dover were formed by shells of a marine organism killed by coccolithoviruses.

Accepted Answer

A) True 
 B)False

Question 3

There is a 1788bp sequence in the middle of the genome of PBCV-1,a phycodnavirus,that does not code for any proteins.What is the function of this region of the genome?

Accepted Answer

A)  It contains 11 tRNA genes.
B)  It is the origin of DNA replication.
C)  It is an enhancer involved in regulating gene expression.
D)  It is a packaging sequence involved in insertion of the viral genome into the capsid.
E)  None of the above.

Question 4

The primary capsid protein of the phycodnavirus PBCV-1,Vp54,is glycosylated.Which of the following describes how the viral protein is thought to acquire its sugar residues?

Accepted Answer

A)  The sugars are added to the protein inside the lumen of the rough ER.
B)  Cellular enzymes in the cytoplasm add the sugars to the capsid protein.
C)  Viral enzymes add the sugars directly to the capsid protein.
D)  The sugars are added to the protein in the Golgi of the host cell.
E)  The sugars are added by viral enzymes after release of the virion from the host cell.

Question 5

One of the reasons why the phcyodnaviruses are so diverse is that their hosts are ancient and equally as diverse.

Accepted Answer

A) True 
 B)False

Question 6

Upon infection with a coccolithovirus,the microalgal host cell may switch from the usual diploid life stage to a haploid cell.Which of the following describes the advantage this has for the host cell?

Accepted Answer

A)  The haploid cell can not replicate the viral genome,so no new viruses are produced.
B)  The haploid cell produces a barrier that prevents virus particles from entering.
C)  The haploid cell can swim away from virus infested waters.
D)  The haploid cell can fuse with other haploid cells,producing virus resistant strains.
E)  The haploid cell does not produce the host cell receptor for virus entry.

Question 7

Which of the following characteristics distinguishes the coccolithoviruses from the chloroviruses,which are both member of the phycodnavirus family?

Accepted Answer

A)  Only the coccolithoviruses have a virion with an internal envelope.
B)  Only the coccolithoviruses are predicted to encode over 300 proteins.
C)  Only the coccolithoviruses replicate entirely in the nucleus of the host cell.
D)  Only the coccolithoviruses encode their own DNA polymerase.
E)  Only the coccolithoviruses encode their own RNA polymerase. E

Question 8

The coccolithoviruses encode enzymes that produce the sphingolipid ceramide.What is the proposed function of this lipid in infected cells?

Accepted Answer

A)  It enhances the production of cellular membranes,which the virus requires for replication.
B)  It modifies cellular membranes,which enhances binding and entry of virions.
C)  It activates apoptosis,causing host cells to lyse and release virus particles.
D)  It inhibits apoptosis,allowing host cells to stay alive longer.
E)  It induces signaling pathways in the host cell that increase viral replication.

Question 9

Chloroviruses,like PBCV-1,encode enzymes which can produce hyaluronan and chitin,two different saccharide polymers.

Accepted Answer

A) True 
 B)False

Question 10

The enzymes encoded by the phycodnavirus PBCV-1 are notable because they are the largest known enzymes of their type found in a viral genome.

Accepted Answer

A) True 
 B)False

Question 11

The virion of the chlorovirus PBCV-1 has a spike located at one of the 12 pentameric vertices.Which of the following describes the function of this spike?

Accepted Answer

A)  It represents the point in the capsid where the DNA is packaged into the virion.
B)  It attaches to the host cell and initiates entry of the virion.
C)  It contains enzymes at its outer tip that degrade the cell wall of the host.
D)  It is an important intermediate in the assembly of the capsid.
E)  It is the point of attachment between the internal lipid envelope and the outer capsid.

Question 12

Which of the following describes the primary distinguishing feature of the prasinoviruses?

Accepted Answer

A)  They have the largest virions of any known virus.
B)  They have the largest genome of any known virus.
C)  They produce more virions per round of replication than any known virus.
D)  They infect the smallest free-living eukaryotic cell.
E)  They only replicate inside the nucleus of their host cell.

Question 13

Which of the following statements describes a characteristic of the late genes of the phycodnavirus PBCV-1?

Accepted Answer

A)  They are only transcribed after DNA synthesis has begun.
B)  They are transcribed by the host cell RNA polymerase.
C)  They encode structural proteins.
D)  They were detected by hybridizing RNA to probes of each viral gene.
E)  All of the above are characteristics of late genes.

Question 14

The genome of the giant mimivirus contains more non-coding and "junk" DNA than most other DNA viruses.

Accepted Answer

A) True 
 B)False

Question 15

Like most other eukaryotic viruses,the entire virion of the chlorovirus PBCV-1,a phycodnavirus,enters the host cell and releases the viral genome into the nucleus.

Accepted Answer

A) True 
 B)False  False

Question 16

Which of the following represents the group of organisms infected by phycodnaviruses?

Accepted Answer

A)  Insects.
B)  Plants.
C)  Prokaryotic cyanobacteria.
D)  Eukaryotic algae.
E)  Amoeba.

Question 17

The prasinovirus which infects the green alga Ostreococcus only produces 6-15 virus particles per infectious cycle.Which of the following explains why the burst size is so small?

Accepted Answer

A)  The host cell is not big enough to hold any more virus particles without lysing.
B)  The host cell has a hard outer coating that makes it difficult for virus particles to leave the cell.
C)  The host cell dies too quickly to allow more virus particles to be produced.
D)  The cell does not contain enough raw materials to allow production of any more virions.
E)  The host cell produces an inhibitor that halts viral DNA replication after the first few virus genomes are produced. A

Question 18

What does the name "mimivirus" refer to?

Accepted Answer

A)  The name of the person who discovered the virus.
B)  A shortened version of "microbe-mimicking" virus.
C)  Abbreviation of "mega informational monstrous infectious" virus
D)  The name of the host species that the virus infects.
E)  The name of the location where the virus was discovered.

Question 19

Which of the following mechanisms is thought to have caused the mimivirus genome to become so large?

Accepted Answer

A)  Insertion of the genome of another virus into the mimivirus genome.
B)  The insertion of a large transposon into the genome.
C)  Acquisition of new genes from the genome of its host.
D)  Acquisition of large segments of non-coding DNA.
E)  Self-duplication of regions of the genome.

Question 20

Which of the following statements about the phaeoviruses,members of the phycodnavirus family,is FALSE?

Accepted Answer

A)  They infect the multicellular brown algae.
B)  They integrate their viral genome into the host cell genome.
C)  They are found in both marine and freshwater environments.
D)  They only infect the free-swimming gametes of their host.
E)  Productive replication of the virus makes the host sterile.

Exam 27: Viruses of Algae and Mimivirus

Which of the following may explain why mimiviruses encode a high number of DNA repair enzymes?

Correct AnswerverifiedShow Answer

The famous white cliffs of Dover were formed by shells of a marine organism killed by coccolithoviruses.

Correct AnswerverifiedShow Answer

There is a 1788bp sequence in the middle of the genome of PBCV-1,a phycodnavirus,that does not code for any proteins.What is the function of this region of the genome?

Correct AnswerverifiedShow Answer

The primary capsid protein of the phycodnavirus PBCV-1,Vp54,is glycosylated.Which of the following describes how the viral protein is thought to acquire its sugar residues?

Correct AnswerverifiedShow Answer

One of the reasons why the phcyodnaviruses are so diverse is that their hosts are ancient and equally as diverse.

Correct AnswerverifiedShow Answer

Upon infection with a coccolithovirus,the microalgal host cell may switch from the usual diploid life stage to a haploid cell.Which of the following describes the advantage this has for the host cell?

Correct AnswerverifiedShow Answer

Which of the following characteristics distinguishes the coccolithoviruses from the chloroviruses,which are both member of the phycodnavirus family?

Correct AnswerverifiedE

The coccolithoviruses encode enzymes that produce the sphingolipid ceramide.What is the proposed function of this lipid in infected cells?

Correct AnswerverifiedShow Answer

Chloroviruses,like PBCV-1,encode enzymes which can produce hyaluronan and chitin,two different saccharide polymers.

Correct AnswerverifiedShow Answer

The enzymes encoded by the phycodnavirus PBCV-1 are notable because they are the largest known enzymes of their type found in a viral genome.

Correct AnswerverifiedShow Answer

The virion of the chlorovirus PBCV-1 has a spike located at one of the 12 pentameric vertices.Which of the following describes the function of this spike?

Correct AnswerverifiedShow Answer

Which of the following describes the primary distinguishing feature of the prasinoviruses?

Correct AnswerverifiedShow Answer

Which of the following statements describes a characteristic of the late genes of the phycodnavirus PBCV-1?

Correct AnswerverifiedShow Answer

The genome of the giant mimivirus contains more non-coding and "junk" DNA than most other DNA viruses.

Correct AnswerverifiedShow Answer

Like most other eukaryotic viruses,the entire virion of the chlorovirus PBCV-1,a phycodnavirus,enters the host cell and releases the viral genome into the nucleus.

Correct AnswerverifiedFalse

Which of the following represents the group of organisms infected by phycodnaviruses?

Correct AnswerverifiedShow Answer

The prasinovirus which infects the green alga Ostreococcus only produces 6-15 virus particles per infectious cycle.Which of the following explains why the burst size is so small?

Correct AnswerverifiedA

What does the name "mimivirus" refer to?

Correct AnswerverifiedShow Answer

Which of the following mechanisms is thought to have caused the mimivirus genome to become so large?

Correct AnswerverifiedShow Answer

Which of the following statements about the phaeoviruses,members of the phycodnavirus family,is FALSE?

Correct AnswerverifiedShow Answer

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