The Basal region - also known as the core region- is one of two regions found in eukaryotic promoters. The other being the Regulatory region. It is found on or around the Transcription start site and contains the four Core promoter elements -although, not all four are found in all eukaroyutes. They may have a combination of some of the four or just one for example
The function of the basal region can be said to be transcription initiation because it is the minimal region required for transcrption to be initiated. As a result, it can be compared to the Shine dalgarno -10, -35 region found in Prokaryotes.