Lytic cycle Lambda Flashcards
what is the genome organization of lambda (lysogenic)?
linear, dsDNA =48 000bp
what happens to lambda phage DNA after injection into bacteria?
end base pair and gaps are sealled by host DNA ligase to circularize (can circularize because of 5’ complementary overhangs at the end); circularized cohesive ends form cos region
lambda phage family name
siphoviradae
why is circularization important?
it makes late gene cluster (head & tail functions) continous
what is the lytic steps of lambda?
t=0 - phage adsorbs; dna injected
t=3 early mRNA made (regulatory proteins)
t=5 2 classes of delayed EARLY mRna made (DNA replication genes & recombination genes/regulators)
t=6 DNA replication starts
t=8 late mRNA made
t=10 structural proteins made
t=22 phage completed
t=45 lysis
How does T7 regulate gene expression timing?
by making new phage RNAP
How does T4 regulate gene expression timing?
by modifying host RNAP to recognize phage promoters (Asia & mocA)
How does lambda control lytic gene expression timing? type of proteins?
by making proteins that change the transcription of phage genome by RNAP; anti-terminator proteins and repressors
host RNAP trasncribes early genes from promoter right and left. What are those early genes?
promoter left -> N gene
promoter right -> cro gene
What is the N protein? where does it act? what does it do to RNAP?
-anti-terminator protein
-it acts on sites in mRNA called nut sites (N utilization) and on RNAP
-it modifies RNAP so it can transcribe through downstream terminator sequences
why is the activity of N protein crucial?
it allows RNAP to transcribe through the terminator sequence to ensure expression of delayed early genes and expression of Q anti-terminator
what are the delayed early genes
DNA replication genes O & P
what is the cro protein? where does it act? what does it do to gene expression??
-repressor protein
-it binds to operator L & right to block transcription from promoter left and right
-it prevents the expression of lysogenic genes & excessive expression of early DNA replication genes
what is Q protein?where does it act? what does it do to RNAP? what does it do to gene expression??
-anti-terminator protein
-it acts on sites in DNA called qut sites and on RNAP
-modifies RNAP to allow it transcribe through terminator sequences
-ensures expression of head, tail, assembly & lysis genes (late genes)
