The enhancer is the cis-acting nucleotide series to which the transcription factor(s) bind, and which increases transcription of the gene. It is not part of the promoter; the general difference being an enhancer can be moved around every where in the general nearness of the gene (within the number of thousand nucleotides on either side or even within the intron), and it will still function properly. It can be clipped out and spliced back in the backward dierction, and will still operate. The promoter, on the other hand, is the position- and orientation relient. Enhancers are generally around 70-80 bp in length and are found, for instance in the crutial DNA molecules. Some of the enhancers are "conditional" in nature, they improve transcription only under the particualr conditions, for example in the presence of the hormone.