Example: Decapentaplegic (dpp) gene in Drosophila.

• encodes a protein which mediates cell signaling.

• contains tens and  possibly hundreds of enhancers, dispersed along a 50 kb area of the DNA

• enhancers located upstream of transcription initiation site, downstream of promoter site, in exons and introns, and even downstream of polyadenylation site.

• each enhancer regulates the expression of the dpp gene in a different site of the developing fly and at different times in the development.