Negatively charged DNA loops twice around histone octamer (2 each of the positively charged H2A, H2B, H3, and H4) to form nucleosome bead. H1 ties nucleosomes together in a string. (Think of “beads on a string”; H1 is the only histone that is not in the nucleosome core.) In mitosis, DNA condenses to form mitotic chromosomes.
Condensed, transcriptionally inactive (“H eteroC hromatin = H ighly C ondensed.”)
Less condensed, transcriptionally active (Eu = true, “truly transcribed”)