Gene Regulation in Bacteria Flashcards
promoter region
where RNA polymerase binds
operon
functioning unit of genomic DNA containing a cluster of separate coding sequences under control of a single operon
trp operon is _
repressible; bacteria synthesizes its own tryptophan unless tryptophan becomes available
trpR repressor protein
sensory for trp level; can not bind DNA (operator) without tryptophan
tryptophan in trpR repressor
acts as a co-repressor
trpR binding the operator prevents _
RNA polymerase binding
operator
the piece of DNA that the repressor binds to
attenuation
regulation of transcription after the initiation step, causing premature termination of transcription
translation of _ controls transcription in the trp operon
leader sequence
leader sequence
region 3 can base pair with region 2 to allow continuation of transcription or region 4 to termination transcription
if the leader sequence is completely translated _
region 3 will base pair with region 4 and repress the trp operon (tryptophan is present)
control sites of the trp operon
operator and leader
What would happen if codons coding for histidine in the leader sequence were removed?
wouldn’t pass region 1, so 3 will base pair with 4 leading to termination
no glucose but lactose available
lac genes are expressed
high glucose but no lactose
lac operon is off (usual)
both lactose and glucose available
low transcription of lac operon, glucose used first
lac operon is _
inducible; usually off because glucose is present for metabolism
lac operon pathway
no glucose but high lactose leads to production of cAMP –> cAMP binds CAP –> CAP helps RNA polymerase bind promoter –> lac operon is transcribed
regulated genes
expressed only under certain conditions; usually to control cell growth and division as needed by cell
constitutive genes
continuously expressed (housekeeping genes required for protein synthesis)
lacZ
beta-galactosidase; enzyme that breaks lactose into 2 monosaccharides
lacY
transporter
lacI
produces a repressor that inhibits lacZ, lacY, and lacA; binding of lactose (or IPTG) inactivates it
lacI is _
constitutively expressed
