iGenetics 3rd Edition by Peter Russell

Exercise 2

Promoters, enhancers, general transcription factors, activators, coactivators, and repressors that regulate the expression of one gene often have structural features that are similar to those regulating the expression of other genes. Nonetheless, the transcriptional control of a gene can be exquisitely specific: it will be specifically transcribed in some tissues at very defined times. Explore how this specificity arises by addressing the following questions:
a. Distinguish between the functions of promoters and enhancers in transcriptional regulation.
b. Distinguish between the functions of general transcription factors, activators, coactivators, and repressors in transcriptional regulation.
c. What structural features are found in activators, and what role do these play in transcriptional activation?
d. How is the mechanism by which eukaryotic repressors function different from that by which prokaryotic repressors function?
e. How can the same enhancer stimulate as well as quench transcription?
f. Given that several different genes may contain the same types of promoter and enhancer elements, and a number of the proteins that bind these elements contain the same structural features, how is transcriptional specificity generated?