lec 19 - Chromatin modification and gene regulation...

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Chromatin modification and gene regulation Frenster JH, (1965a) "Ultrastructural Continuity Between Active and Repressed Chromatin" . Nature 205: 1341-1342.
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Proliferation (e.g. embryo) Differentiation Stem cell Differentiation Dedifferentiation
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Heterochromatin centromere, telomeres + specific regions (cell-type specific) DNA less accessible -> most genes not transcribed In general, little heterochromatin in non differentiated cells with wide transcriptional potential -> flexibility in pattern of gene expression Large areas of chromosomes are condensed in differentiated cells = highly specialized -> express a fixed set of genes
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Telomeric regions are silent Red: Ethidium bromide (DNA) Green: FISH (Telomeric sequence) FISH Immunofluorescence In yeast, 38 telomeres total, but clustered near the periphery: chromosome positions organized even in interphase nuclei SIR = silent information regulator
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Gene silencing at yeast telomeres SIR2 = histone deacetylase
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Gene silencing at yeast telomeres
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Gene silencing at yeast telomeres large complex DNA inaccessible Heterochromatin induced by binding of Rap1 to telomeric sequences, heterochromatin spreads to adjacent DNA independent of its sequence.
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Role of heterochromatin in gene “silencing” Role of heterochromatin in gene “silencing”:
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This note was uploaded on 12/07/2010 for the course BIO BIOL 200 taught by Professor Frogatto during the Fall '10 term at McGill.

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lec 19 - Chromatin modification and gene regulation...

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