BIO 209 Lecture Notes - Lecture 4: Chromosome, Amine, Nucleosome
13 Oct 2016
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Document Summary
Histones: five classes of proteins, h1, h2a, h2b, h3, and h4, unique amino acid composition. 20-30% of lysine and arginine creates a positive charge at neutral ph: found in all eukaryotes chromosomes in amounts similar to dna concentration, specific molar ratio: 1 h1 : 2h2a : 2h2b : 2h3 : 2h4. 2 molecules each of h2a, h2b, h3, and h4 form an octomer called the nucleosome core: forms an ellipsed bead structure. 14 points of contact: electrostatic interactions- histones positively charged and are interacting with the negatively charged phosphates. 6 nucleosomes per turn: nucleosomes create stacked discs to make the helical shape, linker dna on edges. Zigzag model: nucleosome formed when h1 binds to linker dna, has spring-like movement, linker dna passes through axis of the fiber on outside and crosses through the center axis, different organisms have different lengths of linker dna. Zigzag model typically found in dna with longer linker.
