lecture 4

Question 1

bacteriophage t4

Answer 1

elongated head
whiskers
contractile sheath
tube
fibers
baseplate
dsDNA codes for ~200 proteins

Question 2

receptors for T phage

Answer 2

LPS, polysaccharides, protein or glycoproteins

Question 3

t phage fibers

Answer 3

reversible

Question 4

t phage pins

Answer 4

irreversible

Question 5

t4 phage penetration

Answer 5

baseplate conformational change from hexagon to star, opens like aperture
contractile changes starting from baseplate

Question 6

T4 uncoating

Answer 6

DNA has pilot protein that guise DNA through tube into cytoplasm.

Question 7

some phages do not have

Answer 7

contractile sheath, DNA enters through porin openings and crosses membrane into cytoplasm

Question 8

phages DNA is _____ in capsid and ______ in bacteria

Answer 8

linear in capsid, circular in bacteria

has “sticky ends”

Question 9

effect of biosynthesis

Answer 9

drop in cellular synthesis
drop in RNA synthesis (only viral RNA made)
protein synthesis is constant
decrease then increase in DNA synthesis

Question 10

control is usually at level of _________

Answer 10

transcription

gene is turned on and transcribed so mRNA is made

Question 11

T7 phage

Answer 11

1 capsid protomer
portal
fibers (bind to LPS)
internal tube
gp16 degrades peptidoglycan and acts as pilot protein

Question 12

T7 penetrates the cell and _____ pulls DNa into the cell

Answer 12

the cell’s RNA polymerase

makes mRNA as it pulls in

Question 13

classes of T7 genes

Answer 13

class I- early, controls expression of phage genes and host shutoff
class II- DNA metabolism
class III- vision structure and assembly

Question 14

class III gene expression is regulated by

Answer 14

delayed entry and promoter strength

Question 15

t7 ____ allows lysozyme to contact the cell wall

Answer 15

holin

Question 16

phage replicative cycle

Answer 16

eclipse- time to assemble 1 viral particle
latent- time to release one viral particle
rise- time for all viruses to be released
viral yield- virions per infected cell

Question 17

types of mutations

Answer 17

lethal, conditional, plaque types, changes in host range, surface antigens, drug resistance

Question 18

two subfamilies of Microviridae

Answer 18

microviruses- infect free living bacteria

gokushoviruses- infect obligate intracellular parasitic bacteria

Question 19

ssDNA genomes have

Answer 19

extensive overlap of open reading frames

Question 20

ssDNA first step of replication

Answer 20

generates double stranded replicative form DNA

contains “hairpin” region- site for primosome assembly

Question 21

ssDNA replicative form DNA

Answer 21

is amplified via a rolling circle mechanism

host and viral proteins work together as a helicase

Question 22

procapsids are assembled by

Answer 22

the use of scaffolding proteins

scaffolding protein B is required

Question 23

inviridae phages fd, f1, m13

Answer 23

ssDNA made with rolling circle
DNA-binding proein binds DNA to adhesion points with outer membrane
capsid proteins then attach to DNA as DNA goes through membrane
cell does die- 1000 visions per cycle