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In molecular biology and genetics, upstream and downstream both refer to relative positions of genetic code in DNA or RNA. Each strand of DNA or RNA has a 5' end and a 3' end , so named for the carbon position on the deoxyribose (or ribose ) ring.
The relative positions of structures along strands of nucleic acid, including genes and various protein binding sites, are usually noted as being either upstream (towards the 5′-end) or downstream (towards the 3′-end). (See also upstream and downstream.) Directionality is related to, but different from, sense.
Upstream extracellular signaling transduce a variety of intracellular cascades. [1] Receptors and ligands are common upstream signaling molecules that dictate the downstream elements of the signal pathway. A plethora of different factors affect which ligands bind to which receptors and the downstream cellular response that they initiate.
Upstream and downstream can refer to: Molecular biology. Upstream and downstream (DNA), determining relative positions on DNA; Upstream and downstream (transduction) ...
The 5' UTR is upstream from the coding sequence. Within the 5' UTR is a sequence that is recognized by the ribosome which allows the ribosome to bind and initiate translation. The mechanism of translation initiation differs in prokaryotes and eukaryotes. The 3' UTR is found immediately following the translation stop codon.
As promoters are typically immediately adjacent to the gene in question, positions in the promoter are designated relative to the transcriptional start site, where transcription of DNA begins for a particular gene (i.e., positions upstream are negative numbers counting back from -1, for example -100 is a position 100 base pairs upstream).
The most common position is found upstream of the target gene where it can help repress the transcription of the gene. [4] This distance can vary greatly between approximately -20 bp to -2000 bp upstream of a gene. Certain silencers can be found downstream of a promoter located within the intron or
Silencers are DNA sequences found in the 5′ flanking region of eukaryotic genes, assisting in the silencing of a gene. They can be found upstream, downstream, or within the gene of interest. [3] When repressors bind silencers, they act in a similar fashion as enhancers and bend over to prevent the interaction of RNA polymerase with promoters ...