ABSTRACT
Transcription is the synthesis of RNA using DNA as a template. In vivo, transcription is the first level of gene expression and the predominant level of gene regulation. Additionally, RNA primers for cellular DNA replication are generated by transcription, and transcription plays a major role in the replication cycle of the retroid viruses (q.v.). The components of several bacterial and eukaryotic transcription systems have been defined, allowing the in vitro transcription, and coupled in vitro transcription and translation of cloned genes.
