Viruses

Question 1

What do viruses need to survive?

Answer 1

A host

Question 2

What kind of nucleic acid can a virus have?

Answer 2

DNA or RNA

Question 3

What is a bacteriophage?

Answer 3

virus that infects bacteria

Question 4

What are viruses that do not have envelopes called?

Answer 4

Naked viruses

Question 5

What kind of organisms do phages infect?

Answer 5

Hosts with cell walls

Question 6

What is an early gene?

Answer 6

Expressed immediately after infection and includes any special enzymes required to express viral genes

Question 7

What about a virus determines the specificity of the host it can infect?

Answer 7

the surface of the virus

Question 8

How is a virus taken into a cell?

Answer 8

Receptor Mediated endocytosis or fusion

Question 9

Why might antibodies have a hard time accessing a viral capsid?

Answer 9

due to the envelope as it contains host membrane components

Question 10

What is the outcome of the lytic cycle?

Answer 10

The cell lyses

Question 11

The early gene in the lytic cycle produces which enzyme?

Answer 11

hydrolase

Question 12

Which enzyme is transcribed from the lytic cycle late?

Answer 12

lysozyme

Question 13

What is the phage genome incorporated into the bacterial genome known as in lysogenic cycle?

Answer 13

prophage

Question 14

What is the host called during the lysogenic cycle?

Answer 14

lysogen

Question 15

What makes the prophage silent?

Answer 15

phage encoded repressors that bind to phage promoters

Question 16

What is the outcome of the lysogenic cycle?

Answer 16

prophage activates and excises itself from the host genome. Then enters the lytic cycle

Question 17

What is an advantage to the lytic cycle?

Answer 17

useful for rapidly increasing numbers but host cells are destroyed

Question 18

What is a consequence of the lysogenic cycle?

Answer 18

By excising, it may take part of the host genome with it

Question 19

What is transduction?

Answer 19

process of host genome being packaged with viral genome and can spread to new host. There will be a presence of new DNA

Question 20

Are animal viruses phages?

Answer 20

no

Question 21

how do animal virus enter animal cells?

Answer 21

endocytosis

Question 22

What is the productive cycle of animal viruses?

Answer 22

enveloped virus exits host by budding through but does not destroy cell. The envelope becomes coated with membrane

Question 23

What is a prophage called in animal cells?

Answer 23

Provirus

Question 24

Is there a lysogenic cycle in animal cells?

Answer 24

Yes

Question 25

Do positive RNA viruses need to encode RNA dependent RNA Pol?

Answer 25

yes

Question 26

What kind of RNA genome does positive RNA viruses have?

Answer 26

single stranded RNA genome

Question 27

When does translation occur for positive RNA viruses?

Answer 27

upon entrance into cell and acts directly as mRNA. The genome is effective

Question 28

Negative RNA viruses must carry what polymerase?

Answer 28

RNA dependent RNA Pol and encode it

Question 29

What is negative RNA a template for?

Answer 29

negative mRNA [roduction

Question 30

If host ribosomes translate negative RNA what happens?

Answer 30

useless polypeptides are made

Question 31

Where is the RNA dependent RNA Pol carried in the virus?

Answer 31

The capsid

Question 32

What results from using negative RNA strand for template of RNA dependent RNA Pol?

Answer 32

Positive RNA strand

Question 33

Retroviruses encode what enzyme?

Answer 33

Reverse transcriptase

Question 34

What kind of RNA viruses are retroviruses?

Answer 34

Positive RNA viruses that undergo lysogeny.

Question 35

What does Reverse transcriptase use?

Answer 35

Use RNA to make DNA

Question 36

What are the three retroviral genes?

Answer 36

gag, pol, env

Question 37

What does the gene gag encode?

Answer 37

capsid proteins

Question 38

What does the gene pol encode?

Answer 38

Reverse transcriptase

Question 39

What does the gene env encode?

Answer 39

viral envelope proteins

Question 40

What are subviral particles?

Answer 40

infectious agents smaller and more simple than a virus

Question 41

What are prions?

Answer 41

Subviral self replicating proteins that are shape based. It is a misfolded version of a protein that all ready exists

Question 42

What makes prions hard to destroy?

Answer 42

Misfolded proteins are resistant to degradation by chemicals or heat

Question 43

What makes prion diagnosis difficult?

Answer 43

long incubation periods

Question 44

What are viroids?

Answer 44

short piece of circular single stranded RNA with excessive self complementarity that does not code for proteins