Transcription is the process of synthesizing a sequence of mRNA using a molecule of DNA which is read from the 3' ? 5' direction but synthesized in the 5' ? 3'. It takes place in the nucleus of the cell in eukaryotes and nucleoid in prokaryotes. Check out http://chemistry.about.com/od/biochemistry/a/transcription.htm for a detailed explanation, including its three stages: initiation, elongation, and termination.