Overview Composition DNA - charge histone proteins + charge from Lys and Arg residues H2A, H2B, H3, H4 (core proteins) H1 (linking protein) post-translational modification of histone tails login to view 8 more bullets electrostatic attraction of DNA with histone proteins Organization 10 nm chromatin DNA wraps around dimer of H2A:H2B:H3:H4 called nucleosome sensitive to nuclease activity 30 nm chromatin nucleosomes held together by H1 not sensitive to nuclease activity 30 nm fiber loops further condensation Euchromatin/heterochromatin euchromatin = accessible to transcription 10 nm through 30 nm fiber loops heterochromatin = not accessible to transcription any greater condensation than 30 nm fiber loops condensed to save room