BIOL 200 Lecture Notes - Lecture 13: Histone H3, Histone H2B, Histone H2A
Document Summary
2 levels of organization: chromatin, chromosome. During interphase (mitosis is not taking place) dna exists as a nucleoprotein complex known as chromatin: nucleic acids and proteins (histones) Dna is isolated with an isotonic buffer (same as intracellular salt concentration) is associated with an equal mass of protein: chromatin is half dna and half protein by mass. Chromatin exists in extended and condensed forms. 5 major types of histones: h1, h2a, h2b, h3, h4. Histones are rich in + charged basic amino acids which interact with the - charged phosphate groups in dna. Amino acid sequences of h2a, h2b, h3, and h4 are very highly conserved amongst species (almost identical) Amino acid sequence of h1 is more variable. Nucleosomes consist of a protein core with dna (147 bp) wound around the surface (almost two full turns: protein core = octamer consisting of 2 copies each of the following histones: h2a, h2b,
