In class notes for October 19, 2007

In class notes for October 19, 2007 - Introduction to...

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Introduction to Biological Sciences 110a In class notes for October 19, 2007 Genomes o General Characteristics o Structure organization o Packaging Bacteria Eukaryotes Packaging in Eukaryotes o Organized by hierachial levels of compaction o There are actually two mitotic chromosomes o Level 1 Nucleosomes About 150 bp DNA wrapped 2x around a histone core octamer HCO: made of eight histone proteins, there are two copies each of H2A, H2B, H3, and H4 (these are all proteins) H1- is also found, it stabalizes the entry and exit point All histones have a large number of positively charged side chains o Ex. Lysine, arginine o These stabalize as the DNA wraps around the the HCO o The C and N terminal tails are jutting out from the ball (HCO) If there is a string of nucleosomes, you have DNA in between each molecule, creating the 10nm fiber. o Level 2 30nm fiber The helical arrangement of about 6-8 nucleosomes per turn. Basically the 10nm fiber has been put into a helical arrangement. Stabilization of the 30nm fibers comes from bonds between H1-H1 on separate nucleosomes, and from the +/- charge reaction between H2A and H4. The H2A has the negative and the H4 has the positive, or N tail. o
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In class notes for October 19, 2007 - Introduction to...

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