1. In molecular biology, the stretch of nucleotides of DNA that lie in the 3´ direction from the site of initiation of transcription, which is designated as +1 (remembering the convention that the sequence of a DNA molecule is written from the 5´ end to the 3´ end). Downstream nucleotides are marked with plus signs, e.g., +2, +10. Also, to the 3´ side of a particular gene or sequence of nucleotides.

2. In chemical engineering, those phases of a manufacturing process that follow the biotransformation stage. Usually refers to the recovery and purification of the product of a fermentation process.