This defines the beginning of the elongation phase of transcription. And once that happens the sigma disconnects from the DNA chain. At this point the RNA polymerase is functional and the begins to work. Incoming RNA nucleotides come through a channel in the sigma protein and pairs with the complementary bases of the DNA’s template strand. Then the template strand of the DNA is threaded through the RNA polymerase. The sigma protein first opens DNA’s double helix at the promoter section of the DNA strand.

RNA Polymerase adds ribonucleotides to the template strand based on complementary base pairing, generating an mRNA. Each one is unique and initiates the synthesis of a specific gene, or in some cases several different genes. While there are several sigmas, each for different gene complexes, RNA Polymerase is the same molecule that connects to all the different sigmas. Once the sigma binds to the DNA, transcription begins. The promoter sequence is a specific group of base pairs. The sigma protein recognizes and binds to what is deemed the promoter sequence. In bacteria, several sigmas exists and each one initiates the transcription of a specific sequence of DNA (or gene). Once this sigma protein attaches to the DNA molecule, it serves to guide the RNA polymerase down the template strand. The sigma attaches to one strand of the DNA (the template strand) at a very specific location. Transcription is initiated by the attachment of a protein known as a sigma. And it happens a lot like DNA polymerase, except for the the fact that it does not require a primer before transcription begins Bacteria have a single RNA polymerase, whereas Eukaryotes have three different enzymes. RNA is an enzyme that synthesizes RNA from the template strand of DNA. And then those nucleotides are bonded together with a phosphodiester bond just like DNA is bonded. These nucleotides bond to the template strand via hydrogen bonds after the DNA molecule opens up. However, it doesn’t match it exactly as RNA has uracil (U) instead of thymine (T). The nucleotides of RNA are known as ribonucleotides. Whereas, the non-template or coding strand matches the sequence of the RNA. In transcription, the strand of DNA that is used to synthesize mRNA is known as the template strand.

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