IntroductionDifferences Between Replication and TranscriptionChemistry of TranscriptionRNA Polymerase of ProkaryotesThe Sigma SubunitPromotersProkaryotic TranscriptionEukaryotic RNA PolymerasesTranscriptional Events of Eukaryotic RNAPost-transcriptional ModificationsInhibitors of RNA MetabolismReverse TranscriptionSummaryReview QuestionsReferences