The promoter region is a specific DNA sequence that is responsible for the initiation of transcription. It is located upstream of the transcription start site and contains specific binding sites for RNA polymerase and transcription factors. The promoter region determines the efficiency and specificity of transcription initiation.


The coding region is the part of DNA that is transcribed into mRNA and ultimately translated into a protein. It contains the genetic information that specifies the amino acid sequence of the protein. The coding region is also known as the open reading frame (ORF).


The terminator region is a specific DNA sequence that signals the end of transcription. It is located downstream of the coding region and causes the RNA polymerase to dissociate from the DNA template. The terminator region is important for the proper termination of transcription and preventing read-through transcription.

Overall, the transcription unit is composed of these three regions, with the promoter and terminator regions regulating the initiation and termination of transcription, respectively, while the coding region contains the genetic information necessary for protein synthesis.