In previous chapters, we discussed the evidence indicating that the primary control of gene expression lies at the level of transcription, with regulatory processes determining which genes are transcribed to produce the primary RNA transcript. Compared to prokaryotes, the chromosomes of eukaryotes are larger and undergo greater compaction. To understand gene control processes in compact chromosomes, it is therefore necessary to investigate the mechanisms responsible for transcriptional control in a chromosomal context.<\/p>\n\n\n\n