Transcription is the process of synthesizing RNA from a DNA template.
In the nucleus, the transcription preinitiation complex assembles around the core promoter of a gene, which includes a general transcription factor binding site, here a TATA box, a binding site for the RNA polymerase, and the transcription start site.
Once the necessary components are bound, the preinitiation complex unwinds a short stretch of the DNA upstream of the transcription start site, and RNA polymerase begins producing a new strand of mRNA.
Nucleotides are added one by one, and synthesis of the mRNA occurs in a five prime to three prime direction, reading from the template strand. This newly-created strand of mRNA represents a copy of the information in the coding strand, except the thymidines are replaced by uracils.
Synthesis will continue until a termination sequence is encountered, which will release the newly-made mRNA and allow for further processing.
