Viral Structure/Replication

Question 1

Are virophages a type of virus or something different?

Answer 1

It must have a capsid and a nucleic acid, which can be double-stranded or single-stranded, circular or linear, and DNA or RNA. Virophages are therefore a type of virus.

Question 2

Virophages only

Answer 2

• always smaller than Bacteria and Archaea
• they lack the genes for proteins needed to replicate themselves

Question 3

Non-virophage viruses only

Answer 3

the genetic information can be in the form of DNA or RNA

Question 4

Both virophages and other viruses

Answer 4

• can’t replicate on their own
• don’t belong to the 3 domains
• have a protein capsid surrounding their nucleic acid

Question 5

Neither virophages nor other viruses

Answer 5

• generate energy through mitochondria
• use their own ribosomes to make proteins

Question 6

Double stranded DNA

Answer 6

• DSD viruses have processes of replication, transcription, and translation that are the most similar to those used by cells
• is the genetic material of virophages

Question 7

Retro viruses

Answer 7

contain an RNA-dependent DNA polymerase called reverse transcriptase that is used generate a DNA intermediate

Question 8

Single stranded RNA and double stranded DNA viruses

Answer 8

carry their own nucleic acid polymerases (replicases) to replicate the viral genome with no DNA intermediate

Question 9

Single stranded DNA viruses

Answer 9

have replication that involves first generating a complementary DNA strand

Question 10

Single stranded DNA and double stranded DNA viruses

Answer 10

replicate using DNA polymerases, either their own or from those of the host

Question 11

What is another way that cells have evolved to avoid viral infection?

Answer 11

An attachment receptor on the host cell surface that is recognized by the virus is mutated.

Question 12

Virophages interfere with the life cycle of megaviruses by competing with them for replication enzymes, causing defective megaviruses to be produced. When the life cycle occurs correctly, what are the steps?

Answer 12

• virus attaches to host cell which are mediated by cell surface receptors
• penetration of nucleic acids into host cell and the capsid is discarded
• host cell enzymes and replication machinery are used to synthesize new viral genetic and capsid material
  -newly synthesized viral genomes and capsids are assembled into complete viral particles
• the host cell lyses releasing the newly assembled virus particles

Question 13

The cycle of megaviruses differs from those of bacteria and animals. During which part of the bacteriophage life cycle will the viral genome be replicated in synchrony with the host cell?

Answer 13

lysogenic

Question 14

What structure can the viral genome take?

Answer 14

ss-DNA
ds-DNA
ds-RNA

Question 15

Why does the structure of plant and bacterial cells illustrate the reason for having few enveloped viruses that infect these cells?

Answer 15

Plant and bacterial cells contain cell walls that limit the virus from budding out and obtaining the envelope.

Question 16

Steps in the bacteriophage replication cycle

Answer 16

• attachment
• penetration of the viral nucleic acid
• synthesis of viral nucleic acid and proteins
• assembly and packaging of new viruses
• cell lysis and release of new virions

Question 17

What component(s) make up the structure of a virion?

Answer 17

capsid and genome

Question 18

Some viruses have plus sense RNA genomes. Which of the following could describe one of those viruses?

Answer 18

a virus that contains RNA with the same nucleotide sequence as the functional mRNA that its host cell will translate to produce viral products