Chapter 6

Question 0

Life cycle name of bacteriophages

Answer 0

Lytic life cycle

Question 1

Which cell life cycle has an uncoating process

Answer 1

Productive life cycle of animal viruses

Question 2

List steps of bacteriophage lytic cycle

Answer 2

1-adsorption 
2-penetration
3-maturation
4-release
5-reinfection

Question 4

Describe absorption and adsorption (lytic)

Answer 4

Attachment sites on the phage adsorb to receptor sites on host
Most bacteriophages adsorb to the bacterial cell wall
They can only adsorb to certain hosts

Question 5

Eclipse period (lytic)

Answer 5

Time post penetration where phage genome is inside cell but waiting for a trigger. Not detectable or infectious at this stage

Question 6

Why is there no uncoating stage for bacteriophages?

Lytic

Answer 6

Because only the phage genome enters; they “checked their coats at the door”

Question 7

Why do animal phases need an uncoating stage? (Lytic)

Answer 7

They enter the cell via phagocytosis (due to the lack of cell walls) and therefore keep their coats for a longer time

Question 8

Describe replication in the lytic cycle

Answer 8

Enzymes coded by the phage genome shut down the bacterium’s macromolecular synthesis
The phage then replicates it’s ken genome using the hosts proteins

Question 9

Describe maturation (lytic)

Answer 9

Phage parts assemble around genome, spontaneous coming together due to molecular charge interactions

Question 10

Describe lytic cycle release

Answer 10

Phage coded lysozyme breaks down host peptidoglycan causing osmotic lysis
“Break down the wall and busy out”

Question 11

Describe re infection and burst size (lytic)

Answer 11

Phases released from host cell repeat cycle on surrounding cells
50-200 new phases produced from each infected phage
#=burst size

Question 12

What life cycle do temperate bacteriophages use?

Answer 12

Can either use lytic life cycle or incorporate it’s DNA into host DNA and become a non infectious prophage

Question 13

What is a prophage

Answer 13

No infectious particle formed as a result of viral DNA fusing with host DNA

Question 14

What is the main difference between lytic and lysogenic cycle?

Answer 14

Lysogenic hijacks host proteins rather than shutting down the host cell

Question 15

When do Phases switch from lysogenic to lytic cycle?

Answer 15

Upon receiving a trigger

Question 16

Transduction (lysogenic life cycle)

Answer 16

Transferring of host genes by phage

Question 17

How doe slow life cycles differ from lysis and lysogeny?

Answer 17

Phage reproduce without destroying host, cell doesn’t lyse

Question 18

Restriction endonucleoases

Answer 18

Cleaves DNA that lacks appropriate methylation patters (wasn’t pre-approved)

Question 19

Bacterial host defenses

Answer 19

Genetic resistance
Restriction endonucleoases
CRISPR

Question 20

CRISPR

Answer 20

Bacterial “immune system” mediated by clustered regularly interspace do short palindromic repeats

Question 21

Why can’t viruses be grown in synthetic culture media in labs?

Answer 21

They need host cell

Question 22

Multiplicity of infection

Answer 22

Ratio of phages/infected cells

Question 23

Ghost phage

Answer 23

Empty phage, genome already injected into the cell

Question 24

Describe plaque assay

Answer 24

Phage and host cells are mixed and cultures, places where lytic phage have infected and lysed cells appear clear on plate

Question 25

Viriod

Answer 25

Small circular single stand of infectious RNA

Folded in on itself in semi circle