What type of DNA sequence can exert its effects on the expression of a gene from a distance?

An enhancer is a specific type of DNA sequence that can enhance the transcription of a gene from a distance. Enhancers are often located far from the gene they regulate and can influence gene expression by looping the DNA structure to come into contact with the promoter region of the gene. This interaction facilitates the recruitment of transcription factors and RNA polymerase, thereby increasing the rate of transcription.

Enhancers can function independently of their position relative to the gene they regulate, and they can also work in various orientations. This capacity to act at a distance is a defining characteristic of enhancers, distinguishing them from other regulatory sequences.

Promoters are essential for initiating transcription but are usually situated immediately upstream of the gene they control, thus lacking the distance-effect characteristic found in enhancers. Silencers function similarly to enhancers but are involved in repressing transcription rather than enhancing it. Introns are non-coding regions within a gene that are typically removed during RNA processing and do not exert regulatory effects on gene expression at a distance.