Lecture 20 Epigenetics

Lecture 20 Epigenetics - Lecture 20: Epigenetics C h ro m o...

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Lecture 20: Epigenetics C hro m o tin DNA m e thyla tio n His to ne  m o dific a tio n a nd  his to ne  c o de He te ro c hro m a tin a nd  Euc hro m a tin Po s itio n-e ffe c t va rie g a tio n in  Dro s o phila X-c hro m o s o m e  ina c tiva tio n in  m a m m a ls Twine  s tudy in hum a n A ta le  o f two  m ic e Read: Chapter 12 (page 405-417) Fig. 12.4-7, 12.13a-b
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Epigenetics represents the science for the studying heritable changes in gene expression that operate outside changes in DNA itself There are at least two forms of information in the genome of the cell (both are heritable): A- Genetic information: provides the building block for the manufacture of all Proteins needed for the cell functional activity. B- Epigenetic information: provides additional instruction on how, when and where these information should be used.
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Nucleosomes look like "beads on a string” in the electron microscope Diameter of DNA helix (string) is 20 Å Diameter of nucleosome core (bead) is 100 Å 3 Fig. 12.4
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The nucleosome core is an octamer of two each of histones H2A, H2B, H3, and H4 4 Fig. 12.5 160 bp of DNA wraps twice around a nucleosome core 40 bp of linker DNA connects adjacent nucleosomes Histone H1 associates with linker DNA as it enters and leaves the nucleosome core
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Models of higher-order packaging 100 Å fiber is compacted into 300 Å fiber by supercoiling Results in an additional 6-fold compaction of DNA 5 Fig. 12.7a
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This note was uploaded on 04/03/2012 for the course BSCI 410 taught by Professor Staff during the Spring '08 term at Maryland.

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Lecture 20 Epigenetics - Lecture 20: Epigenetics C h ro m o...

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