Figure: 17-09 Caption: The formation of cAMP from ATP, catalyzed by adenyl cyclase.

Figure: 21-04 Caption: Histone acetyltransferases (HATs) are enzymes that add acetate groups to the tails of histones in nucleosomes of closed chromatin (top left). Action of a HAT complex converts closed chromatin to open chromatin (top right), allowing transcription of mRNA to take place.

Figure: 21-16 Caption: Three mechanisms that might be used to alter nucleosome structure by the ATP hydrolysis-dependent remodeling complex SWI/SNF. (a) DNA–histone contacts may be loosened. (b) The path of the DNA around an unaltered nucleosome core particle may be altered. (c) The conformation of the nucleosome core particle may be altered.

Figure: 21-07 Caption: Upstream organization of several eukaryotic genes, illustrating the variable nature, number, and arrangement of controlling elements.

Figure: 21-11 Caption: DNA looping allows factors that bind to enhancers at a distance from the promoter to interact with regulatory proteins in the transcription complex and to maximize transcription.