STAGE 1: TRANSCRIPTION
Transcription: This is where a DNA strand acts as a template for the formation of an mRNA strand complementary to a section of the DNA sequence. This occurs in the nucleus.
Sequence of events
1. The enzyme DNA helicase breaks the hydrogen bonds between the bases, causing the DNA strands to unwind and separate.
2. The enzyme RNA polymerase attaches to the DNA strand at the beginning of a sequence to be copied.
3. Free RNA nucleotides begin to align opposite the DNA strand according to complimentary base pairs: for example, a free RNA nucleotide with the base uracil will align opposite an adenine base. RNA polymerase moves along the DNA strand, forming bonds and adding RNA nucleotides to a growing RNA strand.
4. This eventually results in the formation of an mRNA strand alongside the unwound portion of DNA.
5. Behind the RNA polymerase, the two DNA strands recoil to form the double helix. When the RNA polymerase reaches a stop signal, it detaches from the DNA and the mRNA strand is released.