1. Background information on transcription in bacteria: Transcription is the process of copying information from the DNA sequence to the RNA sequence. As RNA production is the final outcome, it is also called DNA-dependant RNA synthesis. All types of RNA are transcribed from DNA, including: mRNA that codes for protein tRNA which is involved in translation rRNA which composes part of ribosomes snRNA which is involved in splicing and more less common ones Unlike DNA replication where the entire DNA strand is copied, only short sections of the DNA strand (including coding regions or genes) are transcribed to RNA. Also only one strand is copied/transcribed. Transcription occurs in the 5'-3' direction. As there are no nuclei in bacteria, transcription …show more content…
DNA Strand: Unlike DNA replication where both strands are replicated only one strand is transcribed, transcription also occurs in the 5'-3- direction. The strand that is transcribed is known as the template strand, the anti-sense strand or the non-coding strand. The DNA strand that isn't transcribed will however be the same as the newly synthesized RNA strand (except it will have Uracil instead of Thymine). For this reason the non-template DNA strand is often called the coding strand or sense strand. As both strands can be transcribed separately, each strand contains different sets of genes. In bacteria, protein coding/structural genes of similar function are arranged beside each other along the DNA strand and hence they are transcribed together. These groups of genes are called an operon. Instead of transcribing the entire strand (wasteful), only specific genes are transcribed, and instead of transcribing each gene individually (giving monocistronic mRNAs as in eukaryotes) the operon is transcribed in bacteria producing polycistronic …show more content…
It begins with the RNAP holoenzyme binding to the promoter by recognition through the σ sigma factor. Once RNAP binds to the promoter it forms a closed complex. This is because the hydrogen bonds forming the base-pairs are still attached to each other. These bonds are seperated and the RNAP and DNA strand form an open complx which results in the formation of a transcription bubble (which is similar to the unwound DNA at the replication origion). The bubble is about 12 base-pairs long and it allows for RNA nucleotides to join to the complementary DNA ones in the template strand, forming the new RNA strand, or polymerisation. When RNAP transcribes around 10 base-pairs the sigma factor dissociates from the holoenzyme and the core RNAP enzyme continues