Transcript Gene regulation

Gene regulation in
prokaryotes
March 27, 2006
Inducible transcription: lac operon
Inducible transcription: lac operon
Transcription termination by
attenuation: trp operon
Transcription termination by
attenuation
Two possible basepairing schemes
within the mRNA at
the beginning of the
trp operon
Transcription termination by attenuation
Not enough tryptophan amino
acids causes ribosome to stall
on the mRNA  allows preemptor stemloop to form 
termination does not occur
Moving ribosome  pre-emptor structure
does not form – terminator stemloop
forms – terminates transcription of the
rest of the mRNA
Regulation in phage lambda()
Regulation in phage lambda()