An enhancer can work far from its gene
- The idea
- Predict
- See it
- Why
- Check
The idea
“Control DNA only works right next to its gene, facing the right way.”
Promoters and bacterial operators sit right beside the genes they control. So it's easy to assume all control DNA has to.
The short version
The mistake: Control DNA only works right next to its gene, facing the right way.
What's actually true: An enhancer can work thousands of base pairs from its gene, facing either way, because the DNA loops to bring it to the promoter.
- A promoter sits at the start of a gene, where general transcription factors help RNA polymerase bind.
- An enhancer raises transcription. Activators bind it, and the DNA loops so they touch the proteins at the promoter.
- Because the contact happens in 3D, an enhancer can sit upstream, downstream or in an intron, facing either way.
On the exam: If an enhancer is moved or flipped, picture the DNA looping it to the promoter.