Prokaryote Transcription:

Prokaryote Transcription: Transcription performed by RNA polymerase. mRNA produced is identical to 5’  3’ nontemplate/coding strand (except U replaces T), and complementary to 3’  5’ template strand. 2 main differences in transcription in prokaryotes and eukaryotes: • Prokaryote transcription and translation occur at the same time, separate in eukaryotes due to presence of nucleus. • Eukaryote mRNA undergoes post-translational processing, not in prokaryotes. RNA polymerase separates two strands of DNA in a transient “bubble”. Uses one strand as a template to direct synthesis of complementary RNA sequence. It catalyses phosphodiester bond formation between adjacent nucleotides. Transcription has three stages: First RNA polymerase binds to a promoter site on DNA to form a closed complex. 1. Initiation: RNA polymerase initiates transcription after opening DNA duplex to form a transcription bubble (open complex). 2. Elongation: During elongation the transcription bubble moves along DNA. RNA chain extended in the 5′  3′ direction by adding nucleotides to 3’ end. 3. Termination: When transcription terminates or stops the DNA duplex reforms, and RNA polymerase dissociates at a terminator site.