Chapter 13

Question 1

naked viruses

Answer 1

1. contain nucleocapsid
2. lack envelope
3. more resistant to disinfectant

Question 2

envelope viruses

Answer 2

1. contain nucleocapsid

2. have envelope

Question 3

viral genome

Answer 3

1. can be either DNA or RNA
2. liner or circular or fragmented
3. double or single stranded

Question 4

capsid composition

Answer 4

cover with protein coat –> protein coat is made up of capsomers

Question 5

envelope composition

Answer 5

made up of lipid layer

Question 6

spike –> animal viruses

tail fiber –> phages

Answer 6

(no comment)

Question 7

three types of bacteriophage life cycle

Answer 7

1. lytic phages –> productive infection ALWAYS
2. temperate phages –>
3. filamentous phages –> productive infections not by cell lyse but by inhibit growth of host cell

Question 8

5 steps of lytic phage infection (ex:T4 infection)

Answer 8

1. attachment - tail fiber bind to cell wall or pilli or flagella receptor
2. genome entry and uncoat - lysozyme degrades cell wall -> genome injected
3. synthesis - Early protein made = nuclease degrade host DNA, protein modifies host’s RNA polymerase to not able to recognize its promotor.
   - Late protein made = strutural protein for tail fiber and capsid
4. assembly or maturation - protein capsid form and genome packaged
5. release - cell lyse from lysozyme of phage, new phage particles are released

Question 9

lysogenic path

Answer 9

attachment –> inject phage DNA into bacteria –> prophage is integrated into bacterial chromosome –> cell devide –> excision of phage DNA

Question 10

intergrates phage DNA in bacteria chromosome via ____

Answer 10

specific recombination

Question 11

a ____ protein maintains lysogenic state

Answer 11

repressor

Question 12

Phage induction

Answer 12

allows phage to escape damaged host cell. How? DNA repair is activated by the damage thus activated PROTEASE, and this protease destroy REPRESSOR protein

Question 13

example of phages

Answer 13

lytic phage example T4
temperate phage example lambda phage
filamentous phage example M13

Question 14

steps of filamentous phage infection

Answer 14

1. attach to “F pilli” or bacteria
2. single strand DNA enter cytoplasm of host
3. DNA polymerase of host synthesize complementary strand of phage DNA
4. phage coat protein insert into host cytoplasmic membrane
5. extrusion = phage DNA exit the membrane and host protein coat the phage DNA creating a nucleocapsid

Question 15

acute infection

Answer 15

a. rapid onset

b. short duration

Question 16

persistent infection

Answer 16

a. may or may not have symptoms

b. continues for years or life time

Question 17

persistent infection divides into chronic and latent infection

Answer 17

+ chronic infection - continuous production of low levels of virus particles
+ latent infection - viral genome is silent, can’t be eliminated, can be reactivated

Question 18

proto-oncogenes and tumor supressor genes

Answer 18

govern growth and division of cell –> prevent tumor

Question 19

viral oncogenes

Answer 19

interfere with proto-oncogenes and tumor supressor –> cause tumor