Transcription
When a gene is to be expressed, the base sequence of DNA is copied or transcribed into mRNA (messenger RNA). This process takes place in the nucleus and occurs in a series of stages.
- RNA polymerase moves along the DNA unwinding the strand.
- Hydrogen bonds between base pairs break which allows the unzipping of the double helix.
- As RNA polymerase breaks the bonds, it synthesises a primary transcript of mRNA using RNA nucleotides. These form hydrogen bonds with the exposed DNA strand by complementary base pairing.
- The primary transcript of mRNA is processed to produce a mature transcript of mRNA.
- The mature mRNA transcript is now ready to leave the nucleus and travel to the ribosome.