Transcription
DNA is copied into mRNA in the nucleus.
About this topic
Transcription is the first stage of gene expression, in which a gene's DNA sequence is copied to messenger RNA in the nucleus. RNA polymerase binds a promoter, unwinds the DNA, and builds an mRNA strand complementary to the template strand, using uracil (U) instead of thymine.
In eukaryotes, the mRNA is processed: introns are spliced out, a cap and tail are added. The mature mRNA leaves via nuclear pores to the ribosomes. This allows DNA to remain protected in the nucleus.
Think of photocopying a recipe from a reference book that must never leave the library. RNA polymerase moves along the template strand, adding RNA nucleotides: where DNA has A the RNA gets U, where DNA has T the RNA gets A, and so on. In eukaryotes the first copy is edited: introns are cut out and exons spliced together, and a cap and tail are added before the mRNA leaves the nucleus.
Splicing allows one gene to produce several different proteins. Transcription factors decide whether a gene is copied at all, so cells with the same DNA behave differently. A common error is saying DNA leaves the nucleus; only the mRNA does. Another is forgetting that RNA contains uracil, never thymine.
Key ideas
- RNA polymerase
- Uracil replaces thymine
- mRNA carries the message
Quick check
Use cases: where Transcription helps
- Homework: review the key idea behind Transcription before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Transcription without notes.
- Visual learning: play with the interactive lab to see how Transcription changes when you adjust its inputs.
- Teaching a friend: explain Transcription in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Transcription?
DNA is copied into mRNA in the nucleus.
What will I learn in Transcription?
RNA polymerase. Uracil replaces thymine. mRNA carries the message.
Is Transcription part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Transcription lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Transcription?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.