Promoter (genetics)

![Ten classes of eukaryotic promoters and their representative DNA Patterns. The representative eukaryotic promoter classes are shown in the following sections: (A) AT-based class, (B) CG-based class, (C) ATCG-compact class, (D) ATCG-balanced class, (E) ATCG-middle class, (F) ATCG-less class, (G) AT-less class, (H) CG-spike class, (I) CG-less class and (J) ATspike class.[6]](/uploads/202501/06/Ten_classes_of_eukaryotic_promoters_and_their_representative_K-DNA_patterns3347.jpg)
![Superposition between promoter distributions from Homo sapiens, Drosophila melanogaster, Oryza sativa and Arabidopsis thaliana. Red color areas represent conserved promoter sequences.[19]](/uploads/202501/06/Superposition_between_promoter_distributions3347.png)

In genetics, a promoter is a region of DNA that initiates transcription of a particular gene. Promoters are located near the transcription start sites of genes, on the same strand and upstream on the DNA (towards the 5' region of the sense strand). Promoters can be about 100–1000 base pairs long.