GIGUERE - LECTURE 2 Flashcards
how is transcription regulated in prokaryotes?
what is the general organization of operons
how is expression of the operon determined
how were operator/promoter sequences experimentally identified?
DNA footprint experiments:
protein is incubated with labelled DNA fragment containing sequence where the protein is thought to bind
digestion with DNAse cleaves the DNA backbone in exposed regions, but not where the DNA binding protein is bound
analysis of the DNase digests reveals the location of the protein binding site on the DNA
what does the sugar metabolism operator nagC do?
nacC operator negatively regulates nagE and nagB expression by NagC
what is induction vs repression
induction: increased synthesis of enzymes in response to metabolite
repression: the opposite of induction
what is the main advantage of organizing genes in operons
lac operon function and regulation by lactose
what is the lac repressor and what do its domains bind to
lac operon is controlled by negative regulation
lacI is the repressor
lac operon is palindromic
lac repressor has a DNA binding domain on N terminus
C terminus binds the inducer (lactose)
lac repressor is a tetrameric protein
what does the lac operon look like
what is the mode of action of the Lac repressor in the absence and presence of lactose
what is CAP and what does it do
what control on the lac operon does CAP give when there is low glucose
mode of action of the CAP activator in low vs high glucose
summary of the lac operon regulation
trp (tryptophan) operon characteristics
trp operon in the presence vs absence of tryptophan
trp repressor characteristics
comparison of the lac and the trp operon
negative vs positive control of gene expression
negative control: transcribed unless turned off by repressor
activation is the release from the negative control (only RNA pol needed)
positive control: expressed only if active regulator is present (RNA pol + activator needed)
araBAD operon characteristics
regulation of the araBAD operon by the combined action of CAP and AraC proteins
what is a bacteriophage
what is the structure of a bacteriophage
how do bacteriophages operate?
what is the bacteriophage lytic cycle
what is the bacteriophage lysogenic cycle
lytic vs lysogenic cycle comparison
what decides whether the virus will follow the lytic or lysogenic cycle?
decision to enter lytic or lysogenic cycle is based on the binding of the Ci repressor or Cro to 3 operator regions in the viral genome
how does regulation of the phage lambda cycle happen with Ci and Cro
structure of the Cro protein
structure of the Ci repressor and functions of its termini
new phage particle synthesis control region
what are the relative strengths of the PR and PRM promoter
PR is stronger than PRM and does not need the help of activators to recruit RNA polymerase
the PR promoter at -35 and -10 only has one base that is different from the consensus region
what happens on the gene during the lysogenic stage
what happens on the gene during the lytic stage
how do cells go from the lysogenic to the lytic cycle
what is the structure of the repressor protein of lambda (Ci)
how does the RecA cleavage of the repressor happen
