Fig 1. Central Dogma of prokaryotic cells

Transcription

Transcription is the process in all living organisms that synthesizes RNA from a DNA template. This RNA will later on be used to synthesize proteins through translation. Analogous to DNA polymerase in replication, RNA polymerase creates phosphodiester bonds between ribonucleotides. During elongation, of the RNA chain, ribonucleoside triphosphate is added to the 3’ hydroxyl. This implies that the growth from the 5’ to 3’ end is antiparallel to the DNA template. Initially, the promoter region of DNA is recognized by the sigma factor which signals RNA polymerase to the initiation site. The promotor region found in the much studied E. coli is noted to be TATAAT in the -10 region known as the Prinboiw box. In addition, the TTGACA promoter region is known to be common in the -35 region. The sigma factor is released and transcription continues to grow the RNA chain. Once the termination site (marked by transcription terminators) is reached, transcription ends when RNA polymerase and the newly synthesized RNA is released.

In prokaryotes, polycistronic mRNA is found to encode of several clustered, group of genes in a single mRNA. As a result, several polypeptides are created by a single ribosome. In addition, operons are a group of genes that give rise to these polycistronic mRNA during transcription.