Overview of transcription

(a) Transcription of two genes in opposite directions. Genes 1 and 2 from Figure 8-3 are shown. Gene 1 is transcribed from the bottom strand. The RNA polymerase migrates to the left, reading the template strand in a 3′-to-5′ direction and synthesizing RNA in a 5′-to-3′ direction. Gene 2 is transcribed in the opposite direction, to the right, because the top strand is the template. As transcription proceeds, the 5′ end of the RNA is displaced from the template as the transcription bubble closes behind the polymerase. (b) As gene 1 is transcribed, the phosphate group on the 5′ end of the entering ribonucleotide (U) attaches to the 3′ end of the growing RNA chain. S = sugar.

ANIMATED ART: Animated Art Transcription