Why some genes are highly expressed

The DNA in our cells is folded into millions of small packets, like beads on a string, allowing our two-meter linear DNA genomes to fit into a nucleus of only about 0.01 mm in diameter. However, these molecular beads, called nucleosomes, render DNA 'unreadable'. They thus need to be temporarily displaced to allow genes to be copied ('transcribed') into the messages that are used to make proteins. How cells ensure appropriate access to 'promoter' DNA, the regions where gene transcription begins,