A process in which genetic information in DNA is transcribed to form single stranded mRNA.

This process happens in the nucleus (eukaryotes)

There are three stages:

1. Initiation

2. Elongation

3. Termination

During initiation, the enzyme RNA polymerase binds to the promoter and unwinds the DNA double helix. Only ONE of the strands acts as the template strand and is copied. The other DNA strand is the non-template strand. RNA polymerase initiates RNA synthesis at the starting point (at promoter) on the template strand.

During elongation, the enzyme RNA polymerase moves along the DNA template, unwinding the double helix and adds free RNA nucleotides that are complementary to bases of the DNA template. Cytosine will pair with guanine and adenine will pair with uracil. The complementary bases then joined up to form a single strand of mRNA. The mRNA is synthesized from 5’ – 3’

During termination, the enzyme RNA polymerase reaches the terminator. The pre-mRNA is released and the enzyme RNA polymerase detaches from the template strand of DNA.