bacteriophage lambda genome unit 3 genetics

if CI missing or not binding, what state will PR and PRM be in?

PR- on

PRM- off

if cro is missing or not binding, what state will PR and PRM be in?

PR- off

PRM- on

OR1 is critical for

repression of PR

OR3 shuts off

PRM

CI’s order of affinity for the ORs

OR1→OR2→OR3

OR1 and OR2 binding will do what to PR and PRM

PR- blocked

PRM- activated

OR3 will _____ PRM

turn off

order of cro’s affinity for the ORs

OR3→OR2→OR1

early genes

N and Cro

regulatory genes

CI, Cro, Int, Xis, Q

Cro pathway

represses CI

Q protein produced

late genes expressed (head, tail, lysis proteins)

lytic cycle

CI pathway

CI represses Cro

CI activates its own promoter (Prm)

integrase expressed

viral DNA integrated into host genome

lysogenic cycle

PR has

cro, cII, O, P, Q

PRM has

CI, N, CIII, xis

cro is associated with

PR

CI is associated with

PRM

PRM is what cycle

lysogenic

PR is what cycle

lytic

plaque

zone of lysis (will appear clear)

Plaque forming unit (PFU) per mL

viable lambda/mL

bacterial lawn

uniform, dense layer of bacteria grown on an agar plate, used for studying bacterial growth, antibiotic susceptibility, and bacteriophage activity.

lambda has a _____

large burst size

Nut site

where N binds to prevent termination of transcription

PL transcript, N

antiterminator

PL transcript, CIII

protects activator protein CII

PL transcript, Xis

excise

lysogeny

PL transcript, Int

integrate

lysogeny

Q

DNA anti terminator, causes read through from PR’

Cro binding to cI

binds to three site operator at PR, PL to shut down transcription

SOS system turns RecA into

site specific protease

dimerization of CI to encourage lysogenic cycle

When CI binds to oR1, it represses transcription from pL and pR, respectively. These are promoters for expression of lytic genes. Binding to oR2 stimulates expression of CI itself from the relatively weak pRM

how to exit lysogenic cycle

recA will cleave the site joining globular C and N in the monomer, forcing dimers to change to monomers to maintain equilibruim