Section 2 Pt. 2 Flashcards
Tailed phages have: (which kind of genome)
linear ssDNA
_____ have long, thick, contractile, rigid tails (T4)
Myoviruses
______ have long, non-contractile, flexible tails (λ lambda)
Siphoviruses
______ have short, non-contractile tails (T7)
Podoviruses
Phage T7 is a 1- _______
2- one of the original viruses studied by __________
3- model _____ virus
3- has _____ shape
1- podovirus (short tail)
2- the phage group
3- Model lytic virus
4- icosahedral
Phage T7 can only replicate in cells that ____ _____ have the _____ _____
DO NOT have the F Plasmid
Phage T7 has __ core proteins and ___ tail fibres
3 core proteins and 6 fail fibers
tail fibers of Phage T7 bind to _____ on the outside of the cell and then core proteins are pushed through ___ to let __________
bind to LPS outside the cell
core proteins pushed through tail
Only small amount of DNA goes in at first
DNA of phage T7 is packaged in capsid and it enters the cell in specific order/direction: (2 steps)
1- only ___________ enter after the core goes through envelope
2- cell’s _________ transcibes the first gene and as it moves along is pushes against CM and pulls more genome in
1- only 850 bp of DNA let In from the left end (has a promoter)
2- Cell’s RNA ploymerase
Phage T7 class I protein functions: (3)
1- invade host RNA polymerase (no more host genes expressed)
2- inactivate host restriction enzymes (protects phage DNA)
3- Code for Viral RNA polymerase to make class II and III and pulls genome in
Phage T7 class II protein functions: (2)
1- degradation of host DNA
2- replication of phage DNA
** class II has way more promotors so its forced to make more of them genes
Phage T7 class III protein functions: (3)
1- virion structural protiens
2- cell lysis
3- one of the proteins binds to viral RNA pol and makes it bind to III promotors better than class II
Phage T7 packaging: DNA replication generates copies of DNA with small gaps making ____ _____ ______ combined to make a _________
the end problem
concatemer
Cotacatemer is then ____ into single genomes during DNA packaging in a ______ fashion so that class I end is facing out
cut out, Directional
Temperate bacteriophage Lambda λ discovered in _____ by _______ from Ecoli stain K12
1951, Esther Lederberg
strain K12 is a λ _____ (able to generate lysis) and in it, λ exists as ________
lysogen
prophage
Phage λ (unlike T7 - always lytic) can either enter _____
Lytic cycle or lysogenic cycle
Phage λ has a pattern of organization common in tail phages were ______
genes are lined like how proteins will end up in the particle
Stain λPaPa is a recombinant version that is missing _______ and makes _________ in soft agar
Missing tail fibres
Large plaques (This is because it doesnt have tail fibers that slow it down so it spreads faster)
Strain λPaPa is missing the tail making protein due to a ______ _______
frameshift mutation
receptor on the cell is ——–, which is a maltose transporter expressed in presence of maltose
recognized by J-protein on —– of Ur-λ bringing maltose inside
LamB
tail
Ur-l adsorbs to cells better than the PaPa version will bind and infect cells grown in ________ (PaPa won’t)
glucose
with the use of tail fibers, the phages are much more effective at binding to cells
Strain λPaPa: in the situation where the receptor is present at low amounts, they are _______ of _______ without the tail fibres
incapable of attaching
different phages have tails with different lengths but for any specific ________ phage (long non-contractile flexible tails, e.g. lambda) the particles all have the same tail length
This is because its doesn’t have tail length determining ______ protein
siphovirus
H protein
A ____ _______ protein (more protein = longer tail) in sequences of siphovirus
tape measure protein
siphovirus
Phage λ DNA has 12 nt ssDNA ends called ____ _____ on the ends
Genome circularizes after entering the cell through the complimentary cos sequences
cos sites (cohesion)
Phage λ: after infection and circularization of the DNA, 2 genes are expressed: ____ and _____
those help make more genes such as ___
N and cro
cll
Phage λ: If lysis:
replication, structural and lysis genes turned on
Phage λ: If lysogeny: only 2 genes subsequently expressed – cI and int
– cI and int
DNA integrates (by protein encoded by int), then only cI is expressed during lysogeny
