Upstream and downstream (DNA)
In molecular biology, upstream and downstream both refer to a relative position in DNA or RNA. Each strand of DNA or RNA has a 5' end and a 3' end, so named for the carbons on the deoxyribose ring. Relative to the position on the strand, downstream is the region towards the 3' end of the strand. Since DNA strands run in opposite directions, downstream on one strand is upstream on the other strand.