Practice question

Genomic coordinate system anchors transcription start site as +1 at first incorporated nucleotide. Sequences extending toward 5' direction of coding strand opposite transcription are defined upstream, numbered negatively without zero, harboring promoters and enhancers. Downstream sequences lie beyond +1 toward direction polymerase travels. Defining upstream relative to transcription start site rather than translational start distinguishes transcriptional regulation from translational context, allowing mapping of bacterial -10, -35 elements and eukaryotic TATA box at fixed distances from initiation. This convention universally used for promoter analysis and regulatory element reporting.