Upstream and downstream (DNA)

In the context of molecular biology, "upstream" and "downstream" refer to the relative positions of different sequences within a gene or DNA fragment. 1. **Upstream**: This term refers to the regions of DNA that are located before (in the 5' direction) of a specific reference point, typically the transcription start site of a gene. Upstream regions often contain promoter sequences and other regulatory elements that play crucial roles in the initiation of transcription.