Biology / Unit 6 Bio 1261 short lesson, about 20 seconds
Sigma Factor
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The idea
Sigma factor is a subunit that joins prokaryotic RNA polymerase and directs it to recognize a promoter's specific consensus sequence.
In practice
Sigma factor recognizes conserved sequences upstream of a gene, positioning RNA polymerase to begin transcription at the correct start site.
Where people slip
Sigma factor is needed for promoter recognition only — it detaches once transcription is underway, leaving the core polymerase to continue alone.
Your place on the trail
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