An enhancer boosts transcription but can't start it
- The idea
- Predict
- See it
- Why
- Check
The idea
“The enhancer is where RNA polymerase binds and transcription begins.”
Both are stretches of DNA that proteins bind to switch a gene on. It's easy to file them under one name.
The short version
The mistake: The enhancer is where RNA polymerase binds and transcription begins.
What's actually true: Transcription machinery assembles at the promoter, just before the gene. Activators on an enhancer make that happen more often.
- The promoter is the DNA just upstream of where transcription begins. General transcription factors bind it, then RNA polymerase joins them and starts.
- An enhancer is a short DNA sequence that can sit thousands of bases away, upstream or downstream of the gene. Activator proteins bind it.
- The DNA bends so bound activators reach the machinery at the promoter. Transcription then starts more often.
On the exam: Transcription starts at the promoter. An enhancer, near or far, only changes how often.