Test 3 - Ch's 13, 14

Question 1

Define bacteriophage (phage)

Answer 1

Viruses that infect only bacteria.

Question 2

Define virion

Answer 2

single virus particle

Question 3

What is the capsid made of?

Answer 3

protein

Question 4

Nucleocapsid

Answer 4

the capsid and the nucleic acid together

Question 5

Capsomeres

Answer 5

protein subunits that make up the capsid

Question 6

What are the three types of vision shapes? Describe.

Answer 6

1- icosahedral - flat triangles
2- helical - like a bedspring
3- complex - nucleocapsid, tail (aka sheath), and tail fibers

Question 7

Which type of viruses only have the complex shape?

Answer 7

Phages, NOT animal

Question 8

Naked vs enveloped

Answer 8

Naked virions do not have an envelope, while enveloped have a double layer of lipid outside of the capsid - similar to a cell membrane; attachment spikes may protrude from the envelope

Question 9

Four genome types?

Answer 9

ss DNA, ds DNA, ss RNA, & ds RNA (only viruses)

Question 10

What genes must viruses have to survive?

Answer 10

• genes to make the viral protein coat
• to make copies of the viral genome
• to help them get into and out of the host cells

Question 11

How can viral families be classified?

Answer 11

Created based on genome types (ds DNA), shape (helical), and the prescence/absence of envelope (naked)

Question 12

What are some additional ways only animal viruses can be classified?

Answer 12

Based on their routes of transmission to animals

Question 13

What are some of the routes of transmission for animal viruses?

Answer 13

enteric - fecal-oral route
STD - sexual act
zoonoses- transmitted from animal to human ex rabies
respiratory - aerosol (inhaled droplets)

Question 14

What state is bacteria considered to be in during a latent infection?

Answer 14

lysogenic state

Question 15

What are the five stages of infection for lytic viruses?

Answer 15

attachement, genome entry, synthesis (2 steps), assembly, release

Question 16

What is release by the phage during the “genome entry” stage of the lytic virus cycle?

Answer 16

Lysozyme - an end to help break down peptidoglycan

Question 17

go back to synthesis of t4 phage lifecycle

Answer 17

pg2

Question 18

Prophage

Answer 18

when the latent/temperate phages DNA is incorporated into the bact’s DNA

Question 19

Where does site specific recombination occur in the bact’s genome?

Answer 19

between the terminator and the promoter

Question 20

What does the enzyme excisase do?

Answer 20

acts as a repressor for the phage DNA when inc. into the bact’s genome

Question 21

Why is it sometimes beneficial for bacteria to have a prophage?

Answer 21

Able to produce toxins only phages have the instructions for

Question 22

Lysogenic conversion

Answer 22

when having a prophage changes the phenotype of the host bacterium