Molecular Basis Of Inheritance Practice Test

Promoters and enhancers regulate gene expression at different steps and from different positions. A promoter is the region right at the transcription start site where RNA polymerase II and the general transcription factors assemble to kick off transcription. It directly recruits the machinery needed to begin making RNA. An enhancer, by contrast, can be located far away from the gene—upstream, downstream, or within introns—and serves as a binding platform for activator transcription factors. Through DNA looping, these factors contact the promoter and recruit coactivators and the transcription machinery, boosting the rate of transcription without the enhancer itself initiating transcription. This distance- and orientation-independent mechanism explains how enhancers can modulate expression in a tissue-specific or context-dependent way. So the statement that best captures the difference is that a promoter is the site where transcription is initiated by RNA polymerase binding, while an enhancer is a distal element that increases transcription by looping to the promoter through mediator-like factors.