As discussed in Chapter 1 (Section 1.5), a variety of evidence demonstrates that gene regulation primarily operates at the level of transcription, determining which genes will be transcribed into RNA in specific tissues or in response to specific stimuli. In eukaryotes, such transcriptional control operates in part at the level of chromatin structure so that the DNA that is to be transcribed moves to a more open chromatin structure allowing access to regulatory molecules (see Chapters 4 and 5).<\/p>\n\n\n\n