Final answer:
Enhancers bind to promoters during transcription initiation to regulate the frequency of pre-mRNA synthesis.
Step-by-step explanation:
Enhancers bind to promoters during the initiation of transcription.
Basal transcription factors and other transcription factors bind to enhancers and help regulate the frequency of pre-mRNA synthesis from a gene.
Enhancers affect the efficiency of transcription but are not necessary for transcription to proceed.