LECTURE 9-DNA wrap Chromatin and chromosome structure

LECTURE 9-DNA wrap Chromatin and chromosome structure - DNA...

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DNA packaging summary 1. Problem is packaging 2. Levels of chromatin structure (nucleosomes,  30-nm fiber, loops, bands) 3. Histone code marks active and inactive  sequences 4. DNA elements for chromosome structure  include (ARS), TEL and CEN. 5. CEN promotes the assembly of the  kinetochore, a giant protein complex that  attaches the chromosome to the spindle at  division. High resolution scanning immunogold electron micrograph. Yellow = phosphorylated H3 in the pericentromeric region.
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A severe problem of packaging 8
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A severe problem of packaging
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A severe problem of packaging
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A severe problem of packaging
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Visualizing chromatin breakdown products 1.  Beads-on-a-string (low salt)  2.  30-nm fiber (0.15  M KCl) Electron micrographs of “chromatin”  preparations Beads contained “histones”: H1, H2A, H2B, H3, and H4 
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Packaging proteins discovered by DNase I digests of nuclei 1. Isolate nuclei 2. Partial digest with DNase I (nonspecific  endonuclease) 3. Run agarose gel. 4. Result: Ladder of multiples of 150-200 bp 
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Packaging proteins discovered by DNase I digests of nuclei 1. Isolate nuclei 2. Partial digest with DNase I (nonspecific  endonuclease) 3. Run agarose gel. 4. Result: Ladder of multiples of 150-200 bp  Conclusion: Something is protecting the DNA! Proteins = H1, H2A, H2B, H3 & H4
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Packaging proteins discovered by DNase I digests of nuclei 1. Isolate nuclei 2. Partial digest with DNase I (nonspecific  endonuclease) 3. Run agarose gel. 4. Result: Ladder of multiples of 150-200 bp 
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LECTURE 9-DNA wrap Chromatin and chromosome structure - DNA...

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