Upstream/downstream: These descriptors have different meanings depending on context:

  * In genetics, these are terms used to describe directions on DNA, usually relative to the transcription start site of a gene. DNA sequences that are located in the same direction as the direction of transcription are described as downstream. DNA sequence that are located in the opposite direction of transcription are described as upstream. 
  * In any kind of a pathway, upstream refers to events that occur earlier in the pathway, and downstream refers to events that occur later in the pathway.