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Lecture 17 - Lecture 17 Amine sticks out mine that makes...

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Amine that makes peptide bond Amine sticks out and can react with acetate to produce acetyl Lecture 17 Chromatin Structure DNA of human chromosomes: up to 10cm long Size of nucleus : less than 10 micrometers Problem : How to fit the chromosomes in our nucleus Solution? Packaging: Pack chromosomes into something that takes less space Very elaborate Chromatin exists in extended and condensed forms In Eukaryotes, DNA is associated with proteins Nucleoprotein complex : chromatin Realized that DNA looked organized Biochemically, if you take apart chromosome it’s made up of DNA and proteins 1 | Pa g e
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30 nm Fibres Isolated chromatin under physiological ionic conditions Structure : Very small, complicated and packed Thick fibres Above order of magnitude of a protein Extended Form Low ionic conditions -Uncondensed structure of what was present before -Compact structure has opened up 2 | Pa g e
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Chromatin resembles beads on a string Nucleosomes : Basic units of the chromatin (beads) Linker DNA : Found between each nucleosome Nucleosome Structure : Protein + DNA core wound around its surface Core : Octamer containing two species of H2A, H2B, H3 and H4 Highly conserved in eukaryotes Histones wrapped twice around the protein core Wrapping occurs in the middle Shape : Disk shaped structure made of interlocking histone subunits DNA linker has different histones 3 | Pa g e
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bound to it Chromatin that is being actively transcribed assume this form 30 nm fibers Physiological salt concentration
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