The DNA closes up again after transcription
- The idea
- Predict
- See it
- Why
- Check
The idea
“Once a gene is transcribed, its DNA stays unwound, with the RNA holding the strands apart.”
The strands have to come apart to be read, so it's easy to picture them staying apart afterward, propped open by the RNA.
The short version
The mistake: Once a gene is transcribed, its DNA stays unwound, with the RNA holding the strands apart.
What's actually true: The DNA rewinds right behind RNA polymerase and the RNA peels away, so the gene is unchanged and can be read again.
- RNA polymerase unwinds about a dozen base pairs at a time. This transcription bubble moves along the gene with it.
- The RNA pairs with the template strand only inside the enzyme. Then it peels off, and the DNA strands pair up again.
- Transcription leaves the gene unchanged, so many polymerases can read it at once.
On the exam: Only the bubble inside RNA polymerase is open. The DNA closes behind it.