lecture 5 Flashcards
(24 cards)
ssDNA control is at
the level of translation
translation is controlled by
RNA secondary structures at sites where ribosomes bind
ribosomes translating the gene disrupt
secondary structure, allowing replicase translation
ssRNA replication
simultaneous translation and replication of RNA does not occur
replicase binds to RNA and competes with ribosome
ssRNA maturation
M protein binds RNA then coat proteins form capsid
capsid can form first, but has slow affinity
lysis proteins accumulate and cause lysis
lambda phage
tail fiber binds to a porin used to transport maltose
uncoating requires a maltose permease
lytic phase
phase of lambda phage where cell is actively makes virion
lysogenic phase
phase of lambda phage where the DNA is incorporated into cell DNA and is spread during cell division
lambda phage genome
dsDNA
lambda phage transcription
cl and cro gene products are repressors and compete for the same binding sites
PL and PR are promoters where transcription starts
N is anti terminator and enables RNA polymerase to transcribe past a stop signal
N gene on lambda phage
binds to NUT sequences, activates early gene transcription
lambda lysis
protein R attacks peptidoglycan protein S (holin) forms a pore in the cytoplasmic membrane
an early gene,___, is also a _________
Q is an antiterminator
activates the late genes=structural and cell lysis
lambda phage lysogenic cycle
CI repressor block expression of the lytic system by regulating P(L), P(R), and P(RM) promoters
binds as a dimer to P(R)
activates transcription from P(RM) producing more CI
lambda phage genome
dsDNA starts linear, becomes circular using sticky ends
cos sequences
CI ______ and _____ to form a ______
dimerize and octamerize to form a DNA loop
cleavage of CI repressors in cell with _____ leads to ________ _______
damaged DNA leads to prophage induction
lambda phage process of crossing into lytic phase
induction leads to lytic replication
UV damage activates SOS gene- which activate RecA- RecA breaks dimers- Cro R is made and cell goes lytic
cells must be infect with_____ to go lysogenic
more than one phage
more likely to go lysogenic if small cell
_____ concentration determines lysogeny or lytic
CII
CIII protects CII from protease, CII half-life is a few minutes
CII less stable in metabolically active cells. 90% enter lytic cycle. Inactive cells 90% go lysogenized (dormant with cell).
archaeal viruses
- large majority of viral genes have no detectable homologues other than in closely related viruses, except head-tail viruses, similar to bacteriophages
- most have dsDNA genome, some positively supercoiled
- most have internal or external envelopes
- many have unusual morphologies
- most do not kill host
ATV genome
has circular dsDNA
ATV means
acidianus two-tailed virus
ATV
tails spontaneously elongate
lemon shaped
tails protrude when incubated at 75C+
infection at high temperatures leads to lysogeny
