Diagram illustrating the process of transcription - when a gene is converted to protein

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.

  1. RNA polymerase moves along the DNA unwinding the strand.
  2. Hydrogen bonds between base pairs break which allows the unzipping of the double helix.
  3. 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.
  4. The primary transcript of mRNA is processed to produce a mature transcript of mRNA.
  5. The mature mRNA transcript is now ready to leave the nucleus and travel to the ribosome.