MCB14 - Organisms have vastly different genome size....

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Unformatted text preview: Organisms have vastly different genome size. Spontaneous mutation rate (per bp) is relatively constant . 1 The challenge of DNA packaging Largest human chromosome of ~ 3 x 10 8 bp x 0.34 nm/bp = 10 cm (10-2 meters) A cell nucleus = 1 m (10-6 meters) Therefore the DNA must be compacted at least ~ 10 4-fold 2 Many levels of packaging for eukaryotic DNA The double helix An array of nucleosomes A 30 nm Fber of nucleosomes Euchromatin: loops of 30 nm Fbers allow genes to be expressed Heterochromatin: genes are silenced (packed structure not really known) In mitosis chromosomes need additional condensation to be distributed correctly between dividing cells 3 Packaging can be studied by nuclease digests 1. Isolate nuclei 2. Partial digestion with a sequence non- specifc endonuclease 3. Run agarose gel Result: Ladder oF multiples oF 150-200 bp Conclusion: Nucleosomes are protecting the dsDNA in units oF 150-200 bp....
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This document was uploaded on 09/12/2011.

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MCB14 - Organisms have vastly different genome size....

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