Question

The distinction of “upstream” in a DNA strand lies between

• A. Promoter and Terminator
• B. The last Exon and Terminator
• C. Promoter and Transcription unit
• D. The first Intron and the next Exon

Answer 1

The correct option is C Promoter and Transcription unit

Promoter sequences are DNA sequences that define where transcription of a gene by RNA polymerase begins. RNA polymerase and the necessary transcription factors bind to the promoter sequence and initiate transcription. Since the transcription unit excludes the promoter, and the promoter initiates the transcription of the actual gene; DNA, north (towards the 5' end; left in the image) of the transcription unit, denotes upstream of the gene, and the coding region represents the downstream region. Promoter sequences are thus said to be typically located directly upstream or at the 5' end of the transcription initiation site. Therefore the boundary lies between the promoter and the transcription unit.