Describe the sequence of events in DNA transcription

An enzyme called DNA helicase breaks the hydrogen bonds holding the complimentary base pairs together in a double stranded DNA molecule. This causes the DNA helix to unwind, exposing the unpaired bases. Another enzyme called RNA polymerase binds to a 'promotor' region on the exposed DNA strand and moves downstream, attaching free complementary mRNA nucleotides to the exposed DNA bases. This strand of mRNA is released to form a strand of pre-mRNA. The non-coding regions called introns are removed via RNA 'splicing', resulting in a strand of coding mRNA.