Anatomy and Cell Biology 4411B Lecture Notes - Lecture 4: Cyclic Adenosine Monophosphate, Catabolite Activator Protein, Trp Operon
13 Jun 2012
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Document Summary
Eukaryotic chromosomes have linear dna molecules associated with a large amount of protein. Chromatin is a complex of dna and protein and is found in the nucleus of eu- karyotic cells. The protein:dna mass ratio is 2:1 and the histone:dna mass ratio is 1:1. Chromatin in- cludes several levels of condensation including 10 nm fibres with nucleosomes (bead on a string-like configuration) which offer 7x compaction. This is the primary structural unit and is controlled by histones. His- tones are the units that dna winds around to the form the beads. Has a 3-helix core domain and forms a handshake like arrangement. The tails are n-ter- minal or c-terminal that protrude from the nucleosome through minor groove channels. They are in the ideal location for covalent modifications. It is an octamer made of up h3- Formation of the 30 nm fibers which offer 40x compaction provide the second level of compaction. This is achieved through histone tail-mediated nucleosome-nucleosome in- teractions.
