Transcription is the copying of DNA into complementary mRNA.
Transcription is an important step in protein synthesis and occurs inside the nucleus. It can be broken down into three steps:
Initiation: Enzymes such as RNA polymerase (RNAP) bind to the promoter region of the gene.
A small section of the DNA is unwound, exposing the bases for transcription. Only one strand of the DNA is transcribed and used as a template for protein synthesis.
Elongation: Complementary RNA nucleotides assemble alongside the DNA template. RNA polymerase catalyses the formation of phosphodiester bonds between the RNA nucleotides.
Termination: Transcription ends when RNA polymerase reaches the terminator sequence, a section of non-coding DNA positioned just downstream of the gene.
The terminator sequence causes the polymerase to unbind from the DNA. A single strand of mRNA is released.